74 results on '"Chuan-Feng Li"'
Search Results
2. Nonclassical correlation of cascaded photon pairs emitted from quantum dots.
- Author
-
Chuan-Feng Li, Yang Zou, Jin-Shi Xu, Rong-Chun Ge, and Guang-Can Guo
- Subjects
- *
PHOTON correlation , *QUANTUM dots , *EXCITON theory , *QUANTUM entanglement , *TEMPERATURE - Abstract
We studied the quantum correlation of the photon pairs generated by biexciton cascade decays of self-assembled quantum dots, and determined the correlation sudden-change temperature, which is shown to be independent of the background noise, far lower than the entanglement sudden-death temperature, and therefore, easier to be observed in experiments. The relationship between the fine-structure splitting and the sudden-change temperature is also provided. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
3. Approach to accurately measuring the speed of optical precursors.
- Author
-
Chuan-Feng Li, Zong-Quan Zhou, Heejeong Jeong, and Guang-Can Guo
- Subjects
- *
SPEED of light , *OPTICAL waveguides , *OPTICAL polarization , *DISPERSION (Chemistry) , *PHOTONICS - Abstract
Precursors can serve as a bound on the speed of information with dispersive medium. We propose a method to identify the speed of optical wave fronts using polarization-based interference in a solid-state device, which can bound the accuracy of the speed of wave fronts to less than 10-4 with conventional experimental conditions. Our proposal may have important implications for optical communications and fast information processing. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
4. Experimentally witnessing the initial correlation between an open quantum system and its environment.
- Author
-
Chuan-Feng Li, Jian-Shun Tang, Yu-Long Li, and Guang-Can Guo
- Subjects
- *
QUANTUM dots , *SEMICONDUCTORS , *QUANTUM electronics , *PHOTONS , *OPTICAL waveguides - Abstract
System-environment correlations, which determine the (non-)Markovian character of a dynamical process, is an area of intense interest in the study of open quantum systems. We send photons emitted from a quantum dot sample into a 15-m polarization-maintaining optical fiber to generate different system-environment correlated states and then witness the correlations by observing the growth of trace distances. This experimental scheme of correlation witnessing based on system-environment information flow can also be used for other similar systems. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
5. Ultrasensitive phase estimation with white light.
- Author
-
Chuan-Feng Li, Xiao-Ye Xu, Jian-Shun Tang, Jin-Shi Xu, and Guang-Can Guo
- Subjects
- *
QUANTUM measure theory , *PHASE shift (Nuclear physics) , *LONGITUDINAL method , *FREQUENCY spectra , *WAVELENGTHS , *HALL effect - Abstract
An improvement of the scheme by Brunner and Simon [Phys. Rev. Lett. 105, 010405 (2010)] is proposed in order to show that quantum weak measurements can provide a method to detect ultrasmall longitudinal phase shifts, even with white light. By performing an analysis in the frequency domain, we find that the amplification effect will work as long as the spectrum is large enough, irrespective of the behavior in the time domain. As such, the previous scheme can be notably simplified for experimental implementations. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
6. Experimental Detection of Quantum Coherent Evolution through the Violation of Leggett-Garg-Type Inequalities.
- Author
-
Zong-Quan Zhou, Huelga, Susana F., Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
MATHEMATICAL inequalities , *COHERENCE (Nuclear physics) , *SYMMETRY (Physics) , *QUANTUM theory , *MARKOVIAN jump linear systems - Abstract
We discuss the use of inequalities of the Leggett-Garg type (LGtI) to witness quantum coherence and present the first experimental violation of this type of inequalities using a light-matter interfaced system. By separately benchmarking the Markovian character of the evolution and the translational invariance of the conditional probabilities, the observed violation of a LGtI is attributed to the quantum coherent character of the process. These results provide a general method to benchmark "quantumness" when the absence of memory effects can be independently certified and confirm the persistence of quantum coherent features within systems of increasing complexity. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
7. Revisiting Bohr's principle of complementarity with a quantum device.
- Author
-
Jian-Shun Tang, Yu-Long Li, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
CORRESPONDENCE principle (Quantum mechanics) , *COMPLEMENTARITY (Physics) , *QUANTUM theory , *QUANTUM mechanics , *PHOTONS - Abstract
Bohr's principle of complementarity (BPC) is the cornerstone of quantum mechanics. According to this principle, the total wavelike and particlelike information of a particle is limited by the Englert-Greenberger (EG) duality relation. Here, by introducing a quantum detecting device into the experiment, we find that the limit of the EG duality relation is exceeded because of the interference between the wave and particle properties of the photon. A generalized EG duality relation is further developed. Our work provides a generalization of BPC and gives new insights into quantum mechanics. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
8. Proposed solid-state Faraday anomalous-dispersion optical filter.
- Author
-
Wei-Bin Lin, Zong-Quan Zhou, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
SOLID state physics , *FARADAY effect , *RARE earth ions , *OPTICAL communications , *BANDWIDTHS , *LIGHT filters - Abstract
We propose a Faraday anomalous dispersion optical filter (FADOF) based on a rare-earth ion doped crystal. We present theoretical analyses for the solid-state FADOF transmission. Our theoretical model predicts a maximum transmission efficiency of 71% and a double-peaked transmission spectrum with a bandwidth of 6 GHz under current experimental conditions. Our proposal may have important applications in optical communications. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
9. Experimental demonstration of nonlocal effects in the partial-collapse measurement and reversal process.
- Author
-
Xiao-Ye Xu, Jin-Shi Xu, Chuan-Feng Li, Yang Zon, and Guang-Can Guo
- Subjects
- *
PHOTONS , *INTERFEROMETERS , *TOMOGRAPHY , *BELL'S theorem , *QUANTUM measure theory - Abstract
We demonstrate experimentally the nonlocal reversal of a partial-collapse quantum measurement of a two-photon entangled state. Both the partial-collapse measurement and the reversal operation are implemented in linear optics with two displaced Sagnac interferometers, characterized by single-qubit quantum-process tomography. The recovered state is measured by quantum-state tomography, and its nonlocality is characterized by testing the Bell inequality. Our result will be helpful in quantum communication and quantum error correction. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
10. Experimental Greenberger-Horne-Zeilinger-Type Six-Photon Quantum Nonlocality.
- Author
-
Chao Zhang, Yun-Feng Huang, Zhao Wang, Bi-Heng Liu, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
PHOTON-lepton interactions , *GAUGE bosons , *EINSTEIN-Podolsky-Rosen experiment , *LIGHT quantization , *ELECTRON kinetic energy , *QUANTUM optical phenomena , *QUANTIZATION (Physics) , *QUANTUM theory - Abstract
Quantum nonlocality gives us deeper insight into quantum physics. In addition, quantum nonlocality has been further recognized as an essential resource for device-independent quantum information processing in recent years. Most experiments of nonlocality are performed using a photonic system. However, until now, photonic experiments of nonlocality have involved at most four photons. Here, for the first time, we experimentally demonstrate the six-photon quantum nonlocality in an all-versus-nothing manner based on a high-fidelity (88.4%) six-photon Greenberger-Home-Zeilinger state. Our experiment pushes multiphoton nonlocality studies forward to the six-photon region and might provide a larger photonic system for deviceindependent quantum information protocols. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
11. Quantum Storage of Three-Dimensional Orbital-Angular-Momentum Entanglement in a Crystal.
- Author
-
Zong-Quan Zhou, Yi-Lin Hua, Xiao Liu, Geng Chen, Jin-Shi Xu, Yong-Jian Han, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
ANGULAR momentum (Mechanics) , *IONS , *DOPING agents (Chemistry) , *CRYSTAL chemical bonds , *OPTICAL processors , *NUCLEAR moments - Abstract
Here we present the quantum storage of three-dimensional orbital-angular-momentum photonic entanglement in a rare-earth-ion-doped crystal. The properties of the entanglement and the storage process are confirmed by the violation of the Bell-type inequality generalized to three dimensions after storage (S=2.152±0.033). The fidelity of the memory process is 0.993±0.002, as determined through complete quantum process tomography in three dimensions. An assessment of the visibility of the stored weak coherent pulses in higher-dimensional spaces demonstrates that the memory is highly reliable for 51 spatial modes. These results pave the way towards the construction of high-dimensional and multiplexed quantum repeaters based on solid-state devices. The multimode capacity of rare-earth-based optical processors goes beyond the temporal and the spectral degree of freedom, which might provide a useful tool for photonic information processing. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
12. Experimental Demonstration of the Einstein-Podolsky-Rosen Steering Game Based on the All-Versus-Nothing Proof.
- Author
-
Kai Su, Jin-Shi Xu, Xiang-Jun Ye, Yu-Chun Wu, Jing-Ling Chen, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
EINSTEIN-Podolsky-Rosen paradox , *QUANTUM mechanics , *BELL'S theorem , *FINITE element method , *INFORMATION asymmetry - Abstract
Einstein-Podolsky-Rosen (EPR) steering, a generalization of the original concept of "steering" proposed by Schrodinger, describes the ability of one system to nonlocally affect another system's states through local measurements. Some experimental efforts to test EPR steering in terms of inequalities have been made, which usually require many measurement settings. Analogy to the "all-versus-nothing" (AVN) proof of Bell's theorem without inequalities, testing steerability without inequalities would be more strong and require less resources. Moreover, the practical meaning of steering implies that it should also be possible to, store the state information on the side to be steered, a result that has not yet been experimentally demonstrated. Using a recent AVN criterion for two-qubit entangled states, we experimentally implement a practical steering game using quantum memory. Furthermore, we develop a theoretical method to deal with the noise and finite measurement statistics within the AVN framework and apply it to analyze the experimental data. Our results clearly show the facilitation of the AVN criterion for testing steerability and provide a particularly strong perspective for understanding EPR steering. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
13. Dark-state cooling of a trapped ion using microwave coupling.
- Author
-
Yong Lu, Jian-Qi Zhang, Jin-Ming Cui, Dong-Yang Cao, Shuo Zhang, Yun-Feng Huang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
DARK states (Quantum optics) , *COOLING , *ION traps , *MICROWAVES , *ELECTROMAGNETIC induction , *BANDWIDTHS - Abstract
We propose a dark-state cooling method of trapped ion systems in the Lamb-Dicke limit. By microwave dressing the ion, we can obtain two electromagnetically induced transparency structures. The heating effects caused by the carrier and the blue sideband transition vanish due to electromagnetically induced transparency effects and the final mean phonon numbers can be much lower than the recoil limit. Our scheme is robust to fluctuations of microwave power and laser intensities, which provides a broad cooling bandwidth to cool motional modes of a linear ion chain. Moreover, it is more suitable to cool four-level ions on a large-scale ion chip. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
14. Efficient Experimental Verification of Quantum Gates with Local Operations.
- Author
-
Rui-Qi Zhang, Zhibo Hou, Jun-Feng Tang, Jiangwei Shang, Huangjun Zhu, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM gates , *QUANTUM information science - Abstract
Verifying the correct functioning of quantum gates is a crucial step toward reliable quantum information processing, but it becomes an overwhelming challenge as the system size grows due to the dimensionality curse. Recent theoretical breakthroughs show that it is possible to verify various important quantum gates with the optimal sample complexity of O(1/ε) using local operations only, where ε is the estimation precision. In this Letter, we propose a variant of quantum gate verification (QGV) that is robust to practical gate imperfections and experimentally realize efficient QGV on a 2-qubit controlled-not gate and a 3-qubit Toffoli gate using only local state preparations and measurements. The experimental results show that, by using only 1600 and 2600 measurements on average, we can verify with 95% confidence level that the implemented controlled-not gate and Toffoli gate have fidelities of at least 99% and 97%, respectively. Demonstrating the superior low sample complexity and experimental feasibility of QGV, our work promises a solution to the dimensionality curse in verifying large quantum devices in the quantum era. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
15. Super-resolved Imaging of a Single Cold Atom on a Nanosecond Timescale.
- Author
-
Zhong-Hua Qian, Jin-Ming Cui, Xi-Wang Luo, Yong-Xiang Zheng, Yun-Feng Huang, Ming-Zhong Ai, Ran He, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
ION traps , *OPTICAL limiting , *ATOMS , *SPATIAL resolution , *MICROSCOPY - Abstract
In cold atomic systems, fast and high-resolution microscopy of individual atoms is crucial, since it can provide direct information on the dynamics and correlations of the system. Here, we demonstrate nanosecond-scale two-dimensional stroboscopic pictures of a single trapped ion beyond the optical diffraction limit, by combining the main idea of ground-state depletion microscopy with quantum-state transition control in cold atoms. We achieve a spatial resolution up to 175 nm using a NA=0.1 objective in the experiment, which represents a more than tenfold improvement compared with direct fluorescence imaging. To show the potential of this method, we apply it to observe the secular motion of the trapped ion; we demonstrate a temporal resolution up to 50 ns with a displacement detection sensitivity of 10 nm. Our method provides a powerful tool for probing particle positions, momenta, and correlations, as well as their dynamics in cold atomic systems. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
16. Optimized Detection of High-Dimensional Entanglement.
- Author
-
Xiao-Min Hu, Wen-Bo Xing, Yu Guo, Weilenmann, Mirjam, Aguilar, Edgar A., Xiaoqin Gao, Bi-Heng Liu, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo, Zizhu Wang, and Navascués, Miguel
- Subjects
- *
QUANTUM entanglement , *QUANTUM optics , *QUANTUM information science , *ION traps , *HUMAN information processing - Abstract
Entanglement detection is one of the most conventional tasks in quantum information processing. While most experimental demonstrations of high-dimensional entanglement rely on fidelity-based witnesses, these are powerless to detect entanglement within a large class of entangled quantum states, the so-called unfaithful states. In this Letter, we introduce a highly flexible automated method to construct optimal tests for entanglement detection given a bipartite target state of arbitrary dimension, faithful or unfaithful, and a set of local measurement operators. By restricting the number or complexity of the considered measurement settings, our method outputs the most convenient protocol which can be implemented using a wide range of experimental techniques such as photons, superconducting qudits, cold atoms, or trapped ions. With an experimental quantum optics setup that can prepare and measure arbitrary high-dimensional mixed states, we implement some three-setting protocols generated by our method. These protocols allow us to experimentally certify two- and three-unfaithful entanglement in four-dimensional photonic states, some of which contain well above 50% of noise. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
17. Experimental realization of generalized qubit measurements based on quantum walks.
- Author
-
Yuan-yuan Zhao, Neng-kun Yu, Kurzyński, Paweł, Guo-yong Xiang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
POSITIVE operators , *PHOTONS , *POLARIZATION (Nuclear physics) , *BLOCH equations , *QUBITS - Abstract
We report an experimental implementation of a single-qubit generalized measurement scenario, the positive-operator valued measure (POVM), based on a quantum walk model. The qubit is encoded in a single-photon polarization. The photon performs a quantum walk on an array of optical elements, where the polarization-dependent translation is performed via birefringent beam displacers and a change of the polarization is implemented with the help of wave plates. We implement: (i) trine POVM,i.e., the POVM elements uniformly distributed on an equatorial plane of the Bloch sphere; (ii) symmetric-informationally-complete (SIC) POVM; and (iii) unambiguous discrimination of two nonorthogonal qubit states. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
18. Phase Estimation with Weak Measurement Using a White Light Source.
- Author
-
Xiao-Ye Xu, Kedem, Yaron, Kai Sun, Vaidman, Lev, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
PHASE estimation (Electronics) , *LIGHT emitting diodes , *OPTICAL polarization , *ELLIPTIC polarization , *ULTRASHORT laser pulses , *OPTICAL dispersion , *SENSITIVITY analysis - Abstract
We report results of a high precision phase estimation based on a weak measurement scheme using a commercial light-emitting diode. The method is based on a measurement of the imaginary part of the weak value of a polarization operator. The imaginary part of the weak value appeared due to the measurement interaction itself. The sensitivity of our method is equivalent to resolving light pulses of the order of a attosecond and it is robust against chromatic dispersion. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
19. Realization of Reliable Solid-State Quantum Memory for Photonic Polarization Qubit.
- Author
-
Zong-Quan Zhou, Wei-Bin Lin, Ming Yang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM theory , *PHOTONICS , *OPTICAL polarization , *RARE earth ions , *INFORMATION storage & retrieval systems , *ATOMIC frequency standards - Abstract
Faithfully storing an unknown quantum light state is essential to advanced quantum communication and distributed quantum computation applications. The required quantum memory must have high fidelity to improve the performance of a quantum network. Here we report the reversible transfer of photonic polarization states into collective atomic excitation in a compact solid-state device. The quantum memory is based on an atomic frequency comb (AFC) in rare-earth ion-doped crystals. We obtain up to 0.999 process fidelity for the storage and retrieval process of single-photon-level coherent pulse. This reliable quantum memory is a crucial step toward quantum networks based on solid-state devices. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
20. Pathways for Entanglement-Based Quantum Communication in the Face of High Noise.
- Author
-
Xiao-Min Hu, Chao Zhang, Yu Guo, Fang-Xiang Wang, Wen-Bo Xing, Cen-Xiao Huang, Bi-Heng Liu, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo, Xiaoqin Gao, Pivoluska, Matej, and Huber, Marcus
- Subjects
- *
QUANTUM communication , *QUANTUM noise , *PHOTON pairs , *NOISE , *DEGREES of freedom , *QUBITS , *QUANTUM gates , *PHOTONS - Abstract
Entanglement-based quantum communication offers an increased level of security in practical secret shared key distribution. One of the fundamental principles enabling this security--the fact that interfering with one photon will destroy entanglement and thus be detectable--is also the greatest obstacle. Random encounters of traveling photons, losses, and technical imperfections make noise an inevitable part of any quantum communication scheme, severely limiting distance, key rate, and environmental conditions in which quantum key distribution can be employed. Using photons entangled in their spatial degree of freedom, we show that the increased noise resistance of high-dimensional entanglement can indeed be harnessed for practical key distribution schemes. We perform quantum key distribution in eight entangled paths at various levels of environmental noise and show key rates that, even after error correction and privacy amplification, still exceed 1 bit per photon pair and furthermore certify a secure key at noise levels that would prohibit comparable qubit based schemes from working. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
21. Entangling power of two-qubit gates on mixed states.
- Author
-
Zhe Guan, Huan He, Yong-Jian Han, Chuan-Feng Li, Galve, Fernando, and Guang-Can Guo
- Subjects
- *
QUANTUM entanglement , *QUBITS , *MIXED state (Superconductors) , *UNITARY operators , *QUANTUM theory , *QUANTUM optical phenomena - Abstract
The ability to reach a maximally entangled state from a separable one through the use of a two-qubit unitary operator is analyzed for mixed states. This extension from the known case of pure states shows that there are at least two families of gates which are able to give maximum entangling power for all values of purity. It is notable that one of this gates coincides with a maximum discording one. We give analytical proof that such gate is indeed a perfect entangler at all purities and give numerical evidence for the existence of the second one. Furthermore, we find that there are other gates, many in fact, which are perfect entanglers for a restricted range of purities. This highlights the fact that many perfect entangler gates could in principle be found if a thorough analysis of the full parameter space is performed. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
22. Proposal for generating telecommunication-wavelength entangled photon pairs from a quantum dot by frequency down-conversion.
- Author
-
Yi-Tao Wang, Jian-Shun Tang, Yu-Long Li, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
TELECOMMUNICATION , *QUANTUM dots , *PHOTON pairs , *QUANTUM entanglement , *EXCITON theory , *LITHIUM niobate - Abstract
Fine-structure splitting of the exciton energy levels in a quantum dot introduces an energy difference between the two biexciton decay paths. This energy difference greatly reduces the entanglement of the photon pairs generated via biexciton recombination. Here, we propose a feasible method to eliminate the "which-path" information by using a fast frequency down-conversion technique, which substantially improves the entanglement of the photon pairs. Moreover, the wavelengths of both of the entangled photons can be transferred to the telecommunication band, which makes this method further appropriate for quantum communication. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
23. Nonlocality, Steering, and Quantum State Tomography in a Single Experiment.
- Author
-
Chang-Jiang Huang, Guo-Yong Xiang, Yu Guo, Kang-Da Wu, Bi-Heng Liu, Chuan-Feng Li, Guang-Can Guo, and Armin Tavakoli
- Subjects
- *
QUANTUM states , *QUANTUM correlations , *TOMOGRAPHY , *QUANTUM measurement , *BELL'S theorem , *PHOTONICS - Abstract
We investigate whether paradigmatic measurements for quantum state tomography, namely mutually unbiased bases and symmetric informationally complete measurements, can be employed to certify quantum correlations. For this purpose, we identify a simple and noise-robust correlation witness for entanglement detection, steering, and nonlocality that can be evaluated based on the outcome statistics obtained in the tomography experiment. This allows us to perform state tomography on entangled qutrits, a test of Einstein-Podolsky-Rosen steering and a Bell inequality test, all within a single experiment. We also investigate the trade-off between quantum correlations and subsets of tomographically complete measurements as well as the quantification of entanglement in the different scenarios. Finally, we perform a photonics experiment in which we demonstrate quantum correlations under these flexible assumptions, namely with both parties trusted, one party untrusted and both parties untrusted. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
24. Experimental Demonstration of Instrument-Specific Quantum Memory Effects and Non-Markovian Process Recovery for Common-Cause Processes.
- Author
-
Yu Guo, Philip Taranto, Bi-Heng Liu, Xiao-Min Hu, Yun-Feng Huang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM measurement , *MEMORY - Abstract
The duration, strength, and structure of memory effects are crucial properties of physical evolution. Because of the invasive nature of quantum measurement, such properties must be defined with respect to the probing instruments employed. Here, using a photonic platform, we experimentally demonstrate this necessity via two paradigmatic processes: future-history correlations in the first process can be erased by an intermediate quantum measurement; for the second process, a noisy classical measurement blocks the effect of history. We then apply memory truncation techniques to recover an efficient description that approximates expectation values for multitime observables. Our proof-of-principle analysis paves the way for experiments concerning more general non-Markovian quantum processes and highlights where standard open systems techniques break down. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
25. Experimental investigation of quantum Simpson's paradox.
- Author
-
Yu-Long Li, Jian-Shun Tang, Yi-Tao Wang, Yu-Chun Wu, Yong-Jian Han, Chuan-Feng Li, Guang-Can Guo, Ying Yu, Mi-Feng Li, Guo-Wei Zha, Hai-Qiao Ni, and Zhi-Chuan Niu
- Subjects
- *
QUANTUM theory , *MEDICAL sciences , *PHYSICS experiments , *QUANTUM measurement , *QUANTUM dots , *COMPARATIVE studies - Abstract
The well-known Simpson's paradox, or Yule-Simpson (YS) effect, is often encountered in social-science and medical-science statistics. It occurs when the correlations present in different groups are reversed if the groups are combined. Simpson's paradox also exists in quantum measurements. In this Brief Report, we experimentally realized two analogous effects: the quantum-classical YS effect and the quantum-quantum YS effect in the quantum-dot system. We also compared the probability of obtaining those two effects under identical quantum measurements and found that the quantum-quantum YS effect is more likely to occur than the quantum-classical YS effect. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
26. Photonic Implementation of Quantum Information Masking.
- Author
-
Zheng-Hao Liu, Xiao-Bin Liang, Kai Sun, Qiang Li, Yu Meng, Mu Yang, Bo Li, Jing-Ling Chen, Jin-Shi Xu, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM communication , *QUANTUM states , *KNOWLEDGE transfer , *QUANTUM cryptography - Abstract
Masking of quantum information spreads it over nonlocal correlations and hides it from the subsystems. It is known that no operation can simultaneously mask all pure states [Phys. Rev. Lett. 120, 230501 (2018)], so in what sense is quantum information masking useful? Here, we extend the definition of quantum information masking to general mixed states, and show that the resource of maskable quantum states is far more abundant than the no-go theorem seemingly suggests. Geometrically, the simultaneously maskable states lays on hyperdisks in the state hypersphere, and strictly contains the broadcastable states. We devise a photonic quantum information masking machine using time-correlated photons to experimentally investigate the properties of qubit masking, and demonstrate the transfer of quantum information into bipartite correlations and its faithful retrieval. The versatile masking machine has decent extensibility, and may be applicable to quantum secret sharing and fault-tolerant quantum communication. Our results provide some insights on the comprehension and potential application of quantum information masking. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
27. Operational Resource Theory of Imaginarity.
- Author
-
Kang-Da Wu, Kondra, Tulja Varun, Rana, Swapan, Scandolo, Carlo Maria, Guo-Yong Xiang, Chuan-Feng Li, Guang-Can Guo, and Streltsov, Alexander
- Subjects
- *
WAVE-particle duality , *QUANTUM states , *QUANTUM theory , *COMPLEX numbers , *REAL numbers , *QUBITS - Abstract
Wave-particle duality is one of the basic features of quantum mechanics, giving rise to the use of complex numbers in describing states of quantum systems and their dynamics and interaction. Since the inception of quantum theory, it has been debated whether complex numbers are essential or whether an alternative consistent formulation is possible using real numbers only. Here, we attack this long-standing problem theoretically and experimentally, using the powerful tools of quantum resource theories. We show that, under reasonable assumptions, quantum states are easier to create and manipulate if they only have real elements. This gives an operational meaning to the resource theory of imaginarity. We identify and answer several important questions, which include the state-conversion problem for all qubit states and all pure states of any dimension and the approximate imaginarity distillation for all quantum states. As an application, we show that imaginarity plays a crucial role in state discrimination, that is, there exist real quantum states that can be perfectly distinguished via local operations and classical communication but that cannot be distinguished with any nonzero probability if one of the parties has no access to imaginarity. We confirm this phenomenon experimentally with linear optics, discriminating different two-photon quantum states by local projective measurements. Our results prove that complex numbers are an indispensable part of quantum mechanics. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
28. "Super-Heisenberg" and Heisenberg Scalings Achieved Simultaneously in the Estimation of a Rotating Field.
- Author
-
Zhibo Hou, Yan Jin, Hongzhen Chen, Jun-Feng Tang, Chang-Jiang Huang, Haidong Yuan, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
MAGNITUDE estimation , *STANDARD deviations , *PARAMETER estimation , *UNCERTAINTY , *OPTIMAL control theory , *SIMULTANEOUS equations - Abstract
The Heisenberg scaling, which scales as N-1 in terms of the number of particles or T-1 in terms of the evolution time, serves as a fundamental limit in quantum metrology. Better scalings, dubbed as "super-Heisenberg scaling," however, can also arise when the generator of the parameter involves many-body interactions or when it is time dependent. All these different scalings can actually be seen as manifestations of the Heisenberg uncertainty relations. While there is only one best scaling in the single-parameter quantum metrology, different scalings can coexist for the estimation of multiple parameters, which can be characterized by multiple Heisenberg uncertainty relations. We demonstrate the coexistence of two different scalings via the simultaneous estimation of the magnitude and frequency of a field where the best precisions, characterized by two Heisenberg uncertainty relations, scale as T-1 and T-2, respectively (in terms of the standard deviation). We show that the simultaneous saturation of two Heisenberg uncertainty relations can be achieved by the optimal protocol, which prepares the optimal probe state, implements the optimal control, and performs the optimal measurement. The optimal protocol is experimentally implemented on an optical platform that demonstrates the saturation of the two Heisenberg uncertainty relations simultaneously, with up to five controls. As the first demonstration of simultaneously achieving two different Heisenberg scalings, our study deepens the understanding on the connection between the precision limit and the uncertainty relations, which has wide implications in practical applications of multiparameter quantum estimation. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
29. Experimental demonstration of decoherence-induced spontaneous symmetry breaking.
- Author
-
Yun-Feng Huang, Liang Peng, Li Li, Bi-Heng Liu, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
HAMILTONIAN systems , *SYMMETRY (Physics) , *HAMILTONIAN graph theory , *GRAPH theory , *PHYSICS - Abstract
We experimentally investigate the variations of exchange-symmetry properties of the four Bell states in an exchange-symmetric pure dephasing process with a two-photon system generated from spontaneous parametric down-conversion (SPDC). Experiment results show that under such an exchange-symmetric local-noise Hamiltonian, the exchange-symmetry property remains unchanged for two of the three symmetric Bell states, i.e., the states ∣Φ⟩±=1/√2(∣00⟩±∣11⟩). For the antisymmetric Bell state ∣Ψ⟩-=1/√2(∣01⟩-∣10⟩), the exchange-symmetry property increases and achieves a maximum value of 0.5 at the asymptotic limit. However, for the third exchange-symmetric Bell state ∣Ψ⟩+=1/√2(∣01⟩+∣10⟩), the exchange-symmetry property breaks, surviving with a probability of 0.5 at the asymptotic limit, which provides some evidence supporting such decoherence-induced spontaneous-symmetry-breaking phenomena. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
30. Long-Distance Entanglement Purification for Quantum Communication.
- Author
-
Xiao-Min Hu, Cen-Xiao Huang, Yu-Bo Sheng, Lan Zhou, Bi-Heng Liu, Yu Guo, Chao Zhang, Wen-Bo Xing, Yun-Feng Huang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM communication , *PARAMETRIC downconversion , *QUANTUM entanglement , *LONG-distance running , *PLAY environments - Abstract
High-quality long-distance entanglement is essential for both quantum communication and scalable quantum networks. Entanglement purification is to distill high-quality entanglement from low-quality entanglement in a noisy environment and it plays a key role in quantum repeaters. The previous significant entanglement purification experiments require two pairs of low-quality entangled states and were demonstrated in tabletop. Here we propose and report a high-efficiency and long-distance entanglement purification using only one pair of hyperentangled state. We also demonstrate its practical application in entanglement-based quantum key distribution (QKD). One pair of polarization spatial-mode hyperentanglement was distributed over 11 km multicore fiber (noisy channel). After purification, the fidelity of polarization entanglement arises from 0.771 to 0.887 and the effective key rate in entanglement-based QKD increases from 0 to 0.332. The values of Clauser-Horne-Shimony-Holt inequality of polarization entanglement arises from 1.829 to 2.128. Moreover, by using one pair of hyperentanglement and deterministic controlled-NOT gates, the total purification efficiency can be estimated as 6.6×10³ times than the experiment using two pairs of entangled states with spontaneous parametric down-conversion sources. Our results offer the potential to be implemented as part of a full quantum repeater and large-scale quantum network. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
31. On-Demand Quantum Storage of Photonic Qubits in an On-Chip Waveguide.
- Author
-
Chao Liu, Tian-Xiang Zhu, Ming-Xu Su, You-Zhi Ma, Zong-Quan Zhou, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUBITS , *QUANTUM information science , *QUANTUM communication , *CRYSTAL surfaces , *STORAGE - Abstract
Photonic quantum memory is the core element in quantum information processing (QIP). For the scalable and convenient practical applications, great efforts have been devoted to the integrated quantum memory based on various waveguides fabricated in solids. However, on-demand storage of qubits, which is an essential requirement for QIP, is still challenging to be implemented using such integrated quantum memory. Here we report the on-demand storage of time-bin qubits in an on-chip waveguide memory fabricated on the surface of a 151Eu3+:Y2SiO5 crystal, utilizing the Stark-modulated atomic frequency comb protocol. A qubit storage fidelity of 99.3%±0.2% is obtained with single-photon-level coherent pulses, far beyond the highest fidelity achievable using the classical measure-and-prepare strategy. The developed integrated quantum memory with the on-demand retrieval capability represents an important step toward practical applications of integrated quantum nodes in quantum networks. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
32. Experimental Investigation of Quantum PT-Enhanced Sensor.
- Author
-
Shang Yu, Yu Meng, Jian-Shun Tang, Xiao-Ye Xu, Yi-Tao Wang, Peng Yin, Zhi-Jin Ke, Wei Liu, Zhi-Peng Li, Yuan-Ze Yang, Geng Chen, Yong-Jian Han, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
WIRELESS power transmission , *OPTICAL waveguides , *OVERTIME , *DETECTORS , *QUANTUM mechanics , *QUANTUM communication , *QUANTUM measurement , *ELECTRIC circuits - Abstract
PT-symmetric theory is developed to extend quantum mechanics to a complex region, but it wins its great success first in classical systems, for example, optical waveguides and electric circuits, etc., because there are so many counterintuitive phenomena and striking applications, including unidirectional light transport, PT-enhanced sensors (one kind of exceptional-point-based sensor), and wireless power transfer. However, these phenomena and applications are mostly based on the ability to approach a PT-symmetric broken region, which makes it difficult to transfer them to the quantum regime, since the broken quantum PT-symmetric system has not been constructed effectively, until recently several methods have been raised. Here, we construct a quantum PT-symmetric system assisted by weak measurement, which can effectively transit from the unbroken region to the broken region. The full energy spectrum including the real and imaginary parts is directly measured using weak values. Furthermore, based on the ability of approaching a broken region, we for the first time translate the previously mentioned PT-enhanced sensor into the quantum version, and investigate its various features that are associated to the optimal conditions for sensitivity enhancement. In this experiment, we obtain an enhancement of 8.856 times over the conventional Hermitian sensor. Moreover, by separately detecting the real and imaginary parts of energy splitting, we can derive the additional information of the direction of perturbations. Our work paves the way of leading classical interesting PT phenomena and applications to their quantum counterparts. More generally, since the PT system is a subset of non-Hermitian systems, our work will be also helpful in the studies of general exception point in the quantum regime. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
33. Experimental High-Dimensional Quantum Teleportation.
- Author
-
Xiao-Min Hu, Chao Zhang, Bi-Heng Liu, Yu Cai, Xiang-Jun Ye, Yu Guo, Wen-Bo Xing, Cen-Xiao Huang, Yun-Feng Huang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM teleportation , *QUANTUM states , *TELEPORTATION , *BELL'S theorem - Abstract
Quantum teleportation provides a way to transmit unknown quantum states from one location to another. In the quantum world, multilevel systems which enable high-dimensional systems are more prevalent. Therefore, to completely rebuild the quantum states of a single particle remotely, one needs to teleport multilevel (high-dimensional) states. Here, we demonstrate the teleportation of high-dimensional states in a three-dimensional six-photon system. We exploit the spatial mode of a single photon as the high-dimensional system, use two auxiliary entangled photons to realize a deterministic three-dimensional Bell state measurement. The fidelity of teleportation process matrix is F=0.596±0.037. Through this process matrix, we can prove that our teleportation is both nonclassical and genuine three dimensional. Our work paves the way to rebuild complex quantum systems remotely and to construct complex quantum networks. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
34. Minimizing Backaction through Entangled Measurements.
- Author
-
Kang-Da Wu, Bäumer, Elisa, Jun-Feng Tang, Hovhannisyan, Karen V., Perarnau-Llobet, Martí, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
MEASUREMENT , *STATISTICS , *QUANTUM entanglement - Abstract
When an observable is measured on an evolving coherent quantum system twice, the first measurement generally alters the statistics of the second one, which is known as measurement backaction. We introduce, and push to its theoretical and experimental limits, a novel method of backaction evasion, whereby entangled collective measurements are performed on several copies of the system. This method is inspired by a similar idea designed for the problem of measuring quantum work [Perarnau-Llobet et al., Phys. Rev. Lett. 118, 070601 (2017)]. By using entanglement as a resource, we show that the backaction can be extremely suppressed compared to all previous schemes. Importantly, the backaction can be eliminated in highly coherent processes. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
35. Efficient Generation of High-Dimensional Entanglement through Multipath Down-Conversion.
- Author
-
Xiao-Min Hu, Wen-Bo Xing, Bi-Heng Liu, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo, Erker, Paul, and Huber, Marcus
- Subjects
- *
QUANTUM communication , *QUANTUM states , *SCALABILITY , *GENERATIONS , *LOYALTY - Abstract
High-dimensional entanglement promises to greatly enhance the performance of quantum communication and enable quantum advantages unreachable by qubit entanglement. One of the great challenges, however, is the reliable production, distribution, and local certification of high-dimensional sources of entanglement. In this Letter, we present an optical setup capable of producing quantum states with an exceptionally high level of scalability, control, and quality that, together with novel certification techniques, achieve the highest amount of entanglement recorded so far. We showcase entanglement in 32-spatial dimensions with record fidelity to the maximally entangled state (F=0.933±0.001) and introduce measurement efficient schemes to certify entanglement of formation (EoF=3.728±0.006). Combined with the existing multicore fiber technology, our results will lay a solid foundation for the construction of high-dimensional quantum networks. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
36. Experimental Observation of Coherent-Information Superadditivity in a Dephrasure Channel.
- Author
-
Shang Yu, Yu Meng, Raj B. Patel, Yi-Tao Wang, Zhi-Jin Ke, Wei Liu, Zhi-Peng Li, Yuan-Ze Yang, Wen-Hao Zhang, Jian-Shun Tang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
NOISE - Abstract
We present an experimental approach to construct a dephrasure channel that contains both dephasing and erasure noises and can be used as an efficient tool to study the superadditivity of coherent information. Using a three-fold dephrasure channel, the superadditivity of coherent information is observed, and a substantial gap is found between the zero single-letter coherent information and zero quantum capacity. Particularly, we find that, when the coherent information of n channel uses is zero, with a larger number of channel uses the quantum capacity becomes positive. These phenomena exhibit a more obvious superadditivity of coherent information than previous works and demonstrate a higher threshold for nonzero quantum capacity. Such novel channels built in our experiment also can provide a useful platform to study the nonadditive properties of coherent information and quantum channel capacity. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
37. Experimental Optimal Verification of Entangled States Using Local Measurements.
- Author
-
Wen-Hao Zhang, Chao Zhang, Zhe Chen, Xing-Xiang Peng, Xiao-Ye Xu, Peng Yin, Shang Yu, Xiang-Jun Ye, Yong-Jian Han, Jin-Shi Xu, Geng Chen, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM information science , *QUANTUM states - Abstract
The initialization of a quantum system into a certain state is a crucial aspect of quantum information science. While a variety of measurement strategies have been developed to characterize how well the system is initialized, for a given one, there is in general a trade-off between its efficiency and the accessible information of the quantum state. Conventional quantum state tomography can characterize unknown states while requiring exponentially expensive time-consuming postprocessing. Alternatively, recent theoretical breakthroughs show that quantum state verification provides a technique to quantify the prepared state with significantly fewer samples, especially for multipartite entangled states. In this Letter, we modify the original proposal to be robust to practical imperfections, and experimentally implement a scalable quantum state verification on two-qubit and four-qubit entangled states with nonadaptive local measurements. For all the tested states, the estimated infidelity is inversely proportional to the number of samples, which illustrates the power to characterize a quantum state with a small number of samples. Compared to the globally optimal strategy which requires nonlocal measurements, the efficiency in our experiment is only worse by a small constant factor (< 2.5). We compare the performance difference between quantum state verification and quantum state tomography in an experiment to characterize a four-photon Greenberger-Horne-Zeilinger state, and the results indicate the advantage of quantum state verification in both the achieved efficiency and precision. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
38. Minimal Tradeoff and Ultimate Precision Limit of Multiparameter Quantum Magnetometry under the Parallel Scheme.
- Author
-
Zhibo Hou, Zhao Zhang, Guo-Yong Xiang, Chuan-Feng Li, Guang-Can Guo, Hongzhen Chen, Liqiang Liu, and Haidong Yuan
- Subjects
- *
MAGNETIC field measurements , *MAGNETIC fields , *QUANTUM gates , *QUANTUM computing - Abstract
The precise measurement of a magnetic field is one of the most fundamental and important tasks in quantum metrology. Although extensive studies on quantum magnetometry have been carried out over past decades, the ultimate precision that can be achieved for the estimation of all three components of a magnetic field under the parallel scheme remains unknown. This is largely due to the lack of understandings on the incompatibility of the optimal probe states for the estimation of the three components. Here we provide an approach to characterize the minimal tradeoff among the precisions of multiple parameters that arise from the incompatibility of the optimal probe states, which leads to the identification of the ultimate precision limit for the estimation of all three components of a magnetic field under the parallel scheme. The optimal probe state that achieves the ultimate precision is also explicitly constructed. The obtained precision sets a benchmark on the precision of the multiparameter quantum magnetometry under the parallel scheme, which is of fundamental interest and importance in quantum metrology. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
39. Experimental Investigation of State Distinguishability in Parity-Time Symmetric Quantum Dynamics.
- Author
-
Yi-Tao Wang, Zhi-Peng Li, Shang Yu, Zhi-Jin Ke, Wei Liu, Yu Meng, Yuan-Ze Yang, Jian-Shun Tang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM theory , *QUANTUM states , *PARITY (Physics) , *PHYSICS , *OSCILLATIONS , *PHOTONICS - Abstract
Comprehensive study on parity-time (PT) symmetric systems demonstrates the novel properties and innovative application of non-Hermitian physics in recent years. In the quantum regime, PT symmetric physics exhibits unique quantum dynamical behaviors such as spontaneous state-distinguishability oscillation. However, the construction and control of a PT symmetric quantum system are still challenging, that and restrict the experimental investigation of PT symmetric quantum nature and application. In this Letter, we propose and construct a recycling-structure PT symmetric quantum simulator for the first time, which can effectively simulate the discrete-time dynamical process of a PT symmetric quantum system in both unbroken and broken phases, to be different from our previous work [J.-S. Tang, et al., Nat. Photonics 10, 642 (2016)]. We investigate the dynamical features of quantum state distinguishability based on the PT symmetric simulator. Our results demonstrate the novel PT symmetric quantum dynamics characterized by the periodical oscillation of state distinguishability in the unbroken phase, and the monotonic decay of that in the broken phase. This work also provides a practical experimental platform for the future intensive study of PT symmetric quantum dynamics. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
40. Coherent Control of Nitrogen-Vacancy Center Spins in Silicon Carbide at Room Temperature.
- Author
-
Jun-Feng Wang, Fei-Fei Yan, Qiang Li, Zheng-Hao Liu, He Liu, Guo-Ping Guo, Li-Ping Guo, Xiong Zhou, Jin-Ming Cui, Jian Wang, Zong-Quan Zhou, Xiao-Ye Xu, Jin-Shi Xu, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
CONTROL rooms , *QUANTUM communication , *QUANTUM computing , *TEMPERATURE , *QUBITS , *SILICON carbide - Abstract
Solid-state color centers with manipulatable spin qubits and telecom-ranged fluorescence are ideal platforms for quantum communications and distributed quantum computations. In this work, we coherently control the nitrogen-vacancy (NV) center spins in silicon carbide at room temperature, in which telecom-wavelength emission is detected. We increase the NV concentration sixfold through optimization of implantation conditions. Hence, coherent control of NV center spins is achieved at room temperature, and the coherence time T2 can be reached to around 17.1 μs. Furthermore, an investigation of fluorescence properties of single NV centers shows that they are room-temperature photostable single-photon sources at telecom range. Taking advantage of technologically mature materials, the experiment demonstrates that the NV centers in silicon carbide are promising platforms for large-scale integrated quantum photonics and long-distance quantum networks. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
41. Experimental Optimal Orienteering via Parallel and Antiparallel Spins.
- Author
-
Jun-Feng Tang, Zhibo Hou, Jiangwei Shang, Huangjun Zhu, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
ORIENTEERING , *ORIENTEERS , *QUANTUM measurement , *QUANTUM states , *QUANTUM information science , *QUANTUM entanglement - Abstract
Antiparallel spins are superior in orienteering to parallel spins. This intriguing phenomenon is tied to entanglement associated with quantum measurements rather than quantum states. Using photonic systems, we experimentally realize the optimal orienteering protocols based on parallel spins and antiparallel spins, respectively. The optimal entangling measurements for decoding the direction information from parallel spins and antiparallel spins are realized using photonic quantum walks, which is a useful idea that is of wide interest in quantum information processing and foundational studies. Our experiments clearly demonstrate the advantage of antiparallel spins over parallel spins in orienteering. In addition, entangling measurements can extract more information than local measurements even if no entanglement is present in the quantum states. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
42. Experimental Transmission of Quantum Information Using a Superposition of Causal Orders.
- Author
-
Yu Guo, Xiao-Min Hu, Zhi-Bo Hou, Huan Cao, Jin-Ming Cui, Bi-Heng Liu, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo, and Chiribella, Giulio
- Subjects
- *
TELECOMMUNICATION systems , *QUANTUM theory , *SPACETIME , *SUPERPOSITION (Optics) - Abstract
Communication in a network generally takes place through a sequence of intermediate nodes connected by communication channels. In the standard theory of communication, it is assumed that the communication network is embedded in a classical spacetime, where the relative order of different nodes is well defined. In principle, a quantum theory of spacetime could allow the order of the intermediate points between sender and receiver to be in a coherent superposition. Here we experimentally realize a tabletop simulation of this exotic possibility on a photonic system, demonstrating high-fidelity transmission of quantum information over two noisy channels arranged in a superposition of two alternative causal orders. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
43. Experimental Simultaneous Learning of Multiple Nonclassical Correlations.
- Author
-
Mu Yang, Chang-liang Ren, Yue-chi Ma, Ya Xiao, Xiang-Jun Ye, Lu-Lu Song, Jin-Shi Xu, Man-Hong Yung, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM information science , *QUANTUM states , *QUANTUM correlations , *SUPPORT vector machines , *DECISION trees , *QUANTUM computing , *ARTIFICIAL neural networks - Abstract
Nonclassical correlations can be regarded as resources for quantum information processing. However, the classification problem of nonclassical correlations for quantum states remains a challenge, even for finite-size systems. Although there exists a set of criteria for determining individual nonclassical correlations, a unified framework that is capable of simultaneously classifying multiple correlations is still missing. In this Letter, we experimentally explored the possibility of applying machine-learning methods for simultaneously identifying nonclassical correlations. Specifically, by using partial information, we applied an artificial neural network, support vector machine, and decision tree for learning entanglement, quantum steering, and nonlocality. Overall, we found that, for a family of quantum states, all three approaches can achieve high accuracy for the classification problem. Moreover, the run time of the machine-learning methods to output the state label is experimentally found to be significantly less than that of state tomography. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
44. Demonstrating Quantum Coherence and Metrology that is Resilient to Transversal Noise.
- Author
-
Chao Zhang, Bromley, Thomas R., Yun-Feng Huang, Huan Cao, Wei-Min Lv, Bi-Heng Liu, Chuan-Feng Li, Guang-Can Guo, Cianciaruso, Marco, and Adesso, Gerardo
- Subjects
- *
QUANTUM coherence , *NOISE , *QUANTUM noise , *COMPLEMENT receptors , *METROLOGY , *ERROR correction (Information theory) - Abstract
Quantum systems can be exploited for disruptive technologies but in practice quantum features are fragile due to noisy environments. Quantum coherence, a fundamental such feature, is a basis-dependent property that is known to exhibit a resilience to certain types of Markovian noise. Yet, it is still unclear whether this resilience can be relevant in practical tasks. Here, we experimentally investigate the resilient effect of quantum coherence in a photonic Greenberger-Horne-Zeilinger state under Markovian bit-flip noise, and explore its applications in a noisy metrology scenario. In particular, using up to six-qubit probes, we demonstrate that the standard quantum limit can be outperformed under a transversal noise strength of approximately equal magnitude to the signal, providing experimental evidence of metrological advantage even in the presence of uncorrelated Markovian noise. This work highlights the important role of passive control in noisy quantum hardware, which can act as a low-overhead complement to more traditional approaches such as quantum error correction, thus impacting on the deployment of quantum technologies in real-world settings. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
45. Experimental Measurement-Device-Independent Quantum Steering and Randomness Generation Beyond Qubits.
- Author
-
Yu Guo, Shuming Cheng, Xiaomin Hu, Bi-Heng Liu, En-Ming Huang, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo, and Cavalcanti, Eric G.
- Subjects
- *
QUANTUM information science , *QUANTUM states , *QUBITS , *PHOTON pairs - Abstract
In a measurement-device-independent or quantum-refereed protocol, a referee can verify whether two parties share entanglement or Einstein-Podolsky-Rosen (EPR) steering without the need to trust either of the parties or their devices. The need for trusting a party is substituted by a quantum channel between the referee and that party, through which the referee encodes the measurements to be performed on that party's subsystem in a set of nonorthogonal quantum states. In this Letter, an EPR-steering inequality is adapted as a quantum-refereed EPR-steering witness, and the trust-free experimental verification of higher dimensional quantum steering is reported via preparing a class of entangled photonic qutrits. Further, with two measurement settings, we extract 1.106±0.023 bits of private randomness per every photon pair from our observed data, which surpasses the one-bit limit for projective measurements performed on qubit systems. Our results advance research on quantum information processing tasks beyond qubits. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
46. Direct Measurement of a Nonlocal Entangled Quantum State.
- Author
-
Wei-Wei Pan, Xiao-Ye Xu, Kedem, Yaron, Qin-Qin Wang, Zhe Chen, Jan, Munsif, Kai Sun, Jin-Shi Xu, Yong-Jian Han, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
QUANTUM entanglement , *WAVE functions , *QUANTUM measurement , *QUANTUM mechanics , *DEGREES of freedom , *PHOTON pairs - Abstract
Entanglement and the wave function description are two of the core concepts that make quantum mechanics such a unique theory. A method to directly measure the wave function, using weak values, was demonstrated by Lundeen et al. [Nature 474, 188 (2011)]. However, it is not applicable to a scenario of two disjoint systems, where nonlocal entanglement can be a crucial element, since that requires obtaining weak values of nonlocal observables. Here, for the first time, we propose a method to directly measure a nonlocal wave function of a bipartite system, using modular values. The method is experimentally implemented for a photon pair in a hyperentangled state, i.e., entangled both in polarization and momentum degrees of freedom. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
47. Control-Enhanced Sequential Scheme for General Quantum Parameter Estimation at the Heisenberg Limit.
- Author
-
Zhibo Hou, Rui-Jia Wang, Jun-Feng Tang, Haidong Yuan, Guo-Yong Xiang, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
PARAMETER estimation , *ENERGY harvesting , *OPTICAL control , *QUANTUM gates - Abstract
The advantage of quantum metrology has been experimentally demonstrated for phase estimations where the dynamics are commuting. General noncommuting dynamics, however, can have distinct features. For example, the direct sequential scheme, which can achieve the Heisenberg scaling for the phase estimation under commuting dynamics, can have even worse performances than the classical scheme when the dynamics are noncommuting. Here we realize a scalable optimally controlled sequential scheme, which can achieve the Heisenberg precision under general noncommuting dynamics. We also present an intuitive geometrical framework for the controlled scheme and identify sweet spots in time at which the optimal controls used in the scheme can be prefixed without adaptation, which simplifies the experimental protocols significantly. We successfully implement the scheme up to eight controls in an optical platform and demonstrate a precision near the Heisenberg limit. Our work opens the avenue for harvesting the power of quantum control in quantum metrology, and provides a control-enhanced recipe to achieve the Heisenberg precision under general noncommuting dynamics. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
48. Entanglement Detection by Violations of Noisy Uncertainty Relations: A Proof of Principle.
- Author
-
Yuan-Yuan Zhao, Guo-Yong Xiang, Xiao-Min Hu, Bi-Heng Liu, Chuan-Feng Li, Guang-Can Guo, Schwonnek, René, and Wolf, Ramona
- Subjects
- *
PROOF of concept , *QUANTUM noise , *UNCERTAINTY - Abstract
It is well known that the violation of a local uncertainty relation can be used as an indicator for the presence of entanglement. Unfortunately, the practical use of these nonlinear witnesses has been limited to few special cases in the past. However, new methods for computing uncertainty bounds have become available. Here we report on an experimental implementation of uncertainty-based entanglement witnesses, benchmarked in a regime dominated by strong local noise. We combine the new computational method with a local noise tomography in order to design noise-adapted entanglement witnesses. This proof-of-principle experiment shows that quantum noise can be successfully handled by a fully quantum model in order to enhance the ability to detect entanglement. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
49. Experimental Realization of Robust Self-Testing of Bell State Measurements.
- Author
-
Wen-Hao Zhang, Geng Chen, Xing-Xiang Peng, Xiang-Jun Ye, Peng Yin, Xiao-Ye Xu, Jin-Shi Xu, Chuan-Feng Li, and Guang-Can Guo
- Subjects
- *
PHOTON pairs , *BELL'S theorem - Abstract
Bell state measurements, of which the eigenvectors are in an entangled form, are crucial resources in the construction of quantum networks. Therefore, device-independent certification of a Bell state measurement has significance in the quantum information process because it satisfies the exact demand on security. In this study, we implement a proof-of-concept experiment to certify a Bell state measurement device independently in an entanglement swapping process, namely, self-testing. Instead of preparing a tensor product of two singlets with four photons, multiplex encoding in polarization and spatial modes is utilized to produce two pairs of entangled qubits. As a result, we implement a full Bell state measurement and achieve a high degree of Bell violation on the remaining two qubits, which are required for nontrivial self-testing of a Bell state measurement. Furthermore, our results combine the correlations before and after the swapping; thus, the quality of the performed Bell state measurement can be precisely inferred. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
50. Experimental Validation of Quantum Steering Ellipsoids and Tests of Volume Monogamy Relations.
- Author
-
Chao Zhang, Shuming Cheng, Li Li, Qiu-Yue Liang, Bi-Heng Liu, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo, Hall, Michael J. W., Wiseman, Howard M., and Pryde, Geoff J.
- Subjects
- *
ELLIPSOIDS , *QUBITS - Abstract
The set of all qubit states that can be steered to by measurements on a correlated qubit is predicted to form an ellipsoid--called the quantum steering ellipsoid--in the Bloch ball. This ellipsoid provides a simple visual characterization of the initial two-qubit state, and various aspects of entanglement are reflected in its geometric properties. We experimentally verify these properties via measurements on many different polarization-entangled photonic qubit states. Moreover, for pure three-qubit states, the volumes of the two quantum steering ellipsoids generated by measurements on the first qubit are predicted to satisfy a tight monogamy relation, which is strictly stronger than the well-known monogamy of entanglement for concurrence. We experimentally verify these predictions, using polarization and path entanglement. We also show experimentally that this monogamy relation can be violated by a mixed entangled state, which nevertheless satisfies a weaker monogamy relation. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.