15 results on '"Gammon, Daniel"'
Search Results
2. Direct high resolution resonant Raman scattering measurements of InAs quantum dot dynamic nuclear spin polarization states
- Author
-
Ross, Aaron M., Bracker, Allan S., Yakes, Michael K., Gammon, Daniel, Sham, L. J., and Steel, Duncan G.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Physics - Optics ,Quantum Physics - Abstract
We report on the direct measurement of the electron spin splitting and the accompanying nuclear Overhauser (OH) field, and thus the underlying nuclear spin polarization (NSP) and fluctuation bandwidth, in a single InAs quantum dot under resonant excitation conditions with unprecedented spectral resolution. The electron spin splitting is measured directly via resonant spin-flip single photon Raman scattering detected by superconducting nanowires to generate excitation-emission energy maps. The observed two-dimensional maps reveal an OH field that has a non-linear dependence on excitation frequency. This study provides new insight into earlier reports of so-called avoidance and tracking, showing two distinct NSP responses directly by the addition of a emission energy axis. The data show that the polarization processes depend on which electron spin state is optically driven, with surprising differences in the polarization fluctuations for each case: in one case, a stabilized field characterized by a single-peaked distribution shifts monotonically with the laser excitation frequency resulting in a nearly constant optical interaction strength across a wide detuning range, while in the other case the previously reported avoidance behavior is actually the result of a nonlinear dependence on the laser excitation frequency near zero detuning leading to switching between two distinct mesoscopic nuclear spin states. The magnitude of the field, which is as large as 400 mT, is measured with sub-100 nuclear spin sensitivity. Stable/unstable points of the OH field distribution are observed, resulting from the non-linear feedback loop in the electron-trion-nuclear system. Nuclear spin polarization state switching occurs between fields differing by 160 mT at least as fast as 25 ms. Control experiments indicate that the strain-induced quadrupolar interaction may explain the measured OH fields.
- Published
- 2020
- Full Text
- View/download PDF
3. Direct high-resolution resonant Raman scattering measurements of dynamic nuclear spin polarization states of an InAs quantum dot
- Author
-
Ross, Aaron M, Bracker, Allan S, Yakes, Michael K, Gammon, Daniel, Sham, LJ, and Steel, Duncan G
- Subjects
Quantum Physics ,Physical Sciences ,Condensed Matter Physics ,Chemical sciences ,Engineering ,Physical sciences - Published
- 2020
4. A spin-photon interface using charge-tunable quantum dots strongly coupled to a cavity
- Author
-
Luo, Zhouchen, Sun, Shuo, Karasahin, Aziz, Yakes, Michael K., Carter, Samuel G., Bracker, Allan S., Gammon, Daniel, and Waks, Edo
- Subjects
Quantum Physics ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Charged quantum dots containing an electron or hole spin are bright solid-state qubits suitable for quantum networks and distributed quantum computing. Incorporating such quantum dot spin into a photonic crystal cavity creates a strong spin-photon interface, in which the spin can control a photon by modulating the cavity reflection coefficient. However, previous demonstrations of such spin-photon interfaces have relied on quantum dots that are charged randomly by nearby impurities, leading to instability in the charge state, which causes poor contrast in the cavity reflectivity. Here we demonstrate a strong spin-photon interface using a quantum dot that is charged deterministically with a diode structure. By incorporating this actively charged quantum dot in a photonic crystal cavity, we achieve strong coupling between the cavity mode and the negatively charged state of the dot. Furthermore, by initializing the spin through optical pumping, we show strong spin-dependent modulation of the cavity reflectivity, corresponding to a cooperativity of 12. This spin-dependent reflectivity is important for mediating entanglement between spins using photons, as well as generating strong photon-photon interactions for applications in quantum networking and distributed quantum computing.
- Published
- 2019
- Full Text
- View/download PDF
5. Direct Excitation of a Single Quantum Dot with Cavity-SPDC Photons
- Author
-
Paudel, Uttam, Wong, Jia Jun, Goggin, Michael, Kwiat, Paul, Bracker, Allan S., Yakes, Michael, Gammon, Daniel, and Steel, Duncan
- Subjects
Quantum Physics - Abstract
The ability to generate mode-engineered single photons to interface with disparate quantum systems is of importance for building a quantum network. Here we report on the generation of a pulsed, heralded single photon source with a sub-GHz spectral bandwidth that couples to indium arsenide quantum dots centered at 942 nm. The source is built with a type-II PPKTP down-conversion crystal embedded in a semi-confocal optical cavity and pumped with a 76 MHz repetition rate pulsed laser to emit collinear, polarization-correlated photon pairs resonant with a single quantum dot. In order to demonstrate direct coupling, we use the mode-engineered cavity-SPDC single-photon source to resonantly excite an isolated single quantum dot.
- Published
- 2018
- Full Text
- View/download PDF
6. Scalable in operando strain tuning in nanophotonic waveguides enabling three-quantum dot superradiance
- Author
-
Grim, Joel Q., Bracker, Allan S., Zalalutdinov, Maxim, Carter, Samuel G., Kozen, Alexander C., Kim, Mijin, Kim, Chul Soo, Mlack, Jerome T., Yakes, Michael, Lee, Bumsu, and Gammon, Daniel
- Subjects
Quantum Physics ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The quest for an integrated quantum optics platform has motivated the field of semiconductor quantum dot research for two decades. Demonstrations of quantum light sources, single photon switches, transistors, and spin-photon interfaces have become very advanced. Yet the fundamental problem that every quantum dot is different prevents integration and scaling beyond a few quantum dots. Here, we address this challenge by patterning strain via local phase transitions to selectively tune individual quantum dots that are embedded in a photonic architecture. The patterning is implemented with in operando laser crystallization of a thin HfO$_{2}$ film "sheath" on the surface of a GaAs waveguide. Using this approach, we tune InAs quantum dot emission energies over the full inhomogeneous distribution with a step size down to the homogeneous linewidth and a spatial resolution better than 1 $\mu $m. Using these capabilities, we tune multiple quantum dots into resonance within the same waveguide and demonstrate a quantum interaction via superradiant emission from three quantum dots.
- Published
- 2018
- Full Text
- View/download PDF
7. Generation of frequency sidebands on single photons with indistinguishability from quantum dots
- Author
-
Paudel, Uttam, Burgers, Alexander P., Yakes, Michael K., Bracker, Allan S., Gammon, Daniel, and Steel, Duncan G.
- Subjects
Quantum Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Physics - Optics - Abstract
Generation and manipulation of the quantum state of a single photon is at the heart of many quantum information protocols. There has been growing interest in using phase modulators as quantum optics devices that preserve coherence. In this Letter, we have used an electro-optic phase modulator to shape the state vector of single photons emitted by a quantum dot to generate new frequency components (modes) and explicitly demonstrate that the phase modulation process agrees with the theoretical prediction at a single photon level. Through two-photon interference measurements we show that for an output consisting of three modes (the original mode and two sidebands), the indistinguishability of the mode engineered photon, measured through the secondorder intensity correlation (g2(0)) is preserved. This work demonstrates a robust means to generate a photonic qubit or more complex state (e.g., a qutrit) for quantum communication applications by encoding information in the sidebands without the loss of coherence.
- Published
- 2017
- Full Text
- View/download PDF
8. Non-local nuclear spin quieting in quantum dot molecules: Optically-induced extended two-electron spin coherence time
- Author
-
Chow, Colin M., Ross, Aaron M., Kim, Danny, Gammon, Daniel, Bracker, Allan S., Sham, L. J., and Steel, Duncan G.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Quantum Physics - Abstract
We demonstrate the extension of coherence between all four two-electron spin ground states of an InAs quantum dot molecule (QDM) via non-local suppression of nuclear spin fluctuations in both constituent quantum dots (QDs), while optically addressing only the upper QD transitions. Long coherence times are revealed through dark-state spectroscopy as resulting from nuclear spin locking mediated by the exchange interaction between the QDs. Lineshape analysis provides the first measurement of the quieting of the Overhauser field distribution correlating with reduced nuclear spin fluctuations., Comment: Supplementary materials can be found on the publication page of our website. http://research.physics.lsa.umich.edu/dst/Publications.html
- Published
- 2015
- Full Text
- View/download PDF
9. Cavity-stimulated Raman emission from a single quantum dot spin
- Author
-
Sweeney, Timothy M., Carter, Samuel G., Bracker, Allan S., Kim, Mijin, Kim, Chul Soo, Yang, Lily, Vora, Patrick, Brereton, Peter G., Cleveland, Erin R., and Gammon, Daniel
- Subjects
Quantum Physics ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Solid state quantum emitters have shown strong potential for applications in quantum information, but spectral inhomogeneity of these emitters poses a significant challenge. We address this issue in a cavity-quantum dot system by demonstrating cavity-stimulated Raman spin flip emission. This process avoids populating the excited state of the emitter and generates a photon that is Raman shifted from the laser and enhanced by the cavity. The emission is spectrally narrow and tunable over a range of at least 125 GHz, which is two orders of magnitude greater than the natural linewidth. We obtain the regime in which the Raman emission is spin-dependent, which couples the photon to a long-lived electron spin qubit. This process can enable an efficient, tunable source of indistinguishable photons and deterministic entanglement of distant spin qubits in a photonic crystal quantum network.
- Published
- 2014
- Full Text
- View/download PDF
10. Strong Hyperfine-Induced Modulation of an Optically-Driven Hole Spin in an InAs Quantum Dot
- Author
-
Carter, Samuel G., Economou, Sophia E., Greilich, Alex, Barnes, Edwin, Sweeney, Timothy M., Bracker, Allan S., and Gammon, Daniel
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Quantum Physics - Abstract
Compared to electrons, holes in InAs quantum dots have a significantly weaker hyperfine interaction that leads to less dephasing from nuclear spins. Thus many recent studies have suggested that nuclear spins are unimportant for hole spin dynamics compared to electric field fluctuations. We show that the hole hyperfine interaction can have a strong effect on hole spin coherence measurements through a nuclear feedback effect. The nuclear polarization is generated through a unique process that is dependent on the anisotropy of the hole hyperfine interaction and the coherent precession of nuclear spins, giving rise to strong modulation at the nuclear precession frequency., Comment: 13 pages, 4 figures
- Published
- 2013
- Full Text
- View/download PDF
11. Quantum control of a spin qubit coupled to a photonic crystal cavity
- Author
-
Carter, Samuel G., Sweeney, Timothy M., Kim, Mijin, Kim, Chul Soo, Solenov, Dmitry, Economou, Sophia E., Reinecke, Thomas L., Yang, Lily, Bracker, Allan S., and Gammon, Daniel
- Subjects
Quantum Physics ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
A key ingredient for a quantum network is an interface between stationary quantum bits and photons, which act as flying qubits for interactions and communication. Photonic crystal architectures are promising platforms for enhancing the coupling of light to solid state qubits. Quantum dots can be integrated into a photonic crystal, with optical transitions coupling to photons and spin states forming a long-lived quantum memory. Many researchers have now succeeded in coupling these emitters to photonic crystal cavities, but there have been no demonstrations of a functional spin qubit and quantum gates in this environment. Here we have developed a coupled cavity-quantum dot system in which the dot is controllably charged with a single electron. We perform the initialization, rotation and measurement of a single electron spin qubit using laser pulses and find that the cavity can significantly improve these processes.
- Published
- 2012
- Full Text
- View/download PDF
12. Scalable qubit architecture based on holes in quantum dot molecules
- Author
-
Economou, Sophia E., Climente, Juan I., Badolato, Antonio, Bracker, Allan S., Gammon, Daniel, and Doty, Matthew F.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science ,Quantum Physics - Abstract
Spins confined in quantum dots are a leading candidate for solid-state quantum bits that can be coherently controlled by optical pulses. There are, however, many challenges to developing a scalable multibit information processing device based on spins in quantum dots, including the natural inhomogeneous distribution of quantum dot energy levels, the difficulty of creating all-optical spin manipulation protocols compatible with nondestructive readout, and the substantial electron-nuclear hyperfine interaction-induced decoherence. Here, we present a scalable qubit design and device architecture based on the spin states of single holes confined in a quantum dot molecule. The quantum dot molecule qubit enables a new strategy for optical coherent control with dramatically enhanced wavelength tunability. The use of hole spins allows the suppression of decoherence via hyperfine interactions and enables coherent spin rotations using Raman transitions mediated by a hole-spin-mixed optically excited state. Because the spin mixing is present only in the optically excited state, dephasing and decoherence are strongly suppressed in the ground states that define the qubits and nondestructive readout is possible. We present the qubit and device designs and analyze the wavelength tunability and fidelity of gate operations that can be implemented using this strategy. We then present experimental and theoretical progress toward implementing this design., Comment: 13 pages, 9 figures
- Published
- 2012
- Full Text
- View/download PDF
13. Optical measurement and modeling of interactions between two hole or two electron spins in coupled InAs quantum dots
- Author
-
Greilich, Alex, Bădescu, Ştefan C., Kim, Danny, Bracker, Allan S., and Gammon, Daniel
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Quantum Physics - Abstract
Two electron spins in quantum dots coupled through coherent tunneling are generally acknowledged to approximately obey Heisenberg isotropic exchange. This has not been established for two holes. Here we measure the spectra of two holes and of two electrons in two vertically stacked self-assembled InAs quantum dots using optical spectroscopy as a function of electric and magnetic fields. We find that the exchange is approximately isotropic for both systems, but that significant asymmetric contributions, arising from spin-orbit and Zeeman interactions combined with spatial asymmetries, are required to explain large anticrossings and fine-structure energy splittings in the spectra. Asymmetric contributions to the isotropic Hamiltonian for electrons are of the order of a few percent while those for holes are an order of magnitude larger., Comment: 5 pages, 3 figures
- Published
- 2012
- Full Text
- View/download PDF
14. Ultrafast optical control of entanglement between two quantum dot spins
- Author
-
Kim, Danny, Carter, Samuel G., Greilich, Alex, Bracker, Allan, and Gammon, Daniel
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Quantum Physics - Abstract
The interaction between two quantum bits enables entanglement, the two-particle correlations that are at the heart of quantum information science. In semiconductor quantum dots much work has focused on demonstrating single spin qubit control using optical techniques. However, optical control of entanglement of two spin qubits remains a major challenge for scaling from a single qubit to a full-fledged quantum information platform. Here, we combine advances in vertically-stacked quantum dots with ultrafast laser techniques to achieve optical control of the entangled state of two electron spins. Each electron is in a separate InAs quantum dot, and the spins interact through tunneling, where the tunneling rate determines how rapidly entangling operations can be performed. The two-qubit gate speeds achieved here are over an order of magnitude faster than in other systems. These results demonstrate the viability and advantages of optically controlled quantum dot spins for multi-qubit systems., Comment: 24 pages, 5 figures
- Published
- 2010
- Full Text
- View/download PDF
15. Optical Spin Initialization and Non-Destructive Measurement in a Quantum Dot Molecule
- Author
-
Kim, Danny, Economou, Sophia E., Badescu, Stefan C., Scheibner, Michael, Bracker, Allan S., Bashkansky, Mark, Reinecke, Thomas L., and Gammon, Daniel
- Subjects
Quantum Physics ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The spin of an electron in a self-assembled InAs/GaAs quantum dot molecule is optically prepared and measured through the trion triplet states. A longitudinal magnetic field is used to tune two of the trion states into resonance, forming a superposition state through asymmetric spin exchange. As a result, spin-flip Raman transitions can be used for optical spin initialization, while separate trion states enable cycling transitions for non-destructive measurement. With two-laser transmission spectroscopy we demonstrate both operations simultaneously, something not previously accomplished in a single quantum dot., Comment: Accepted for publication in Phys. Rev. Lett
- Published
- 2008
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.