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The exploration of physical degrees of freedom of light with infinite dimensionality, such as orbital angular momentum (OAM) and frequency, has profoundly reshaped the landscape of modern optics, with representative photonic functional devices including optical vortex emitters and frequency combs. In nanophotonics, whispering gallery mode microresonators naturally support applications based on the OAM of light and have been employed as on-chip emitters of monochromatic optical vortices. On the other hand, whispering gallery mode microresonators can serve as a highly efficient non-linear optical platform for producing light at different frequencies, that is, microcombs. Here we combine optical vortices and microcombs by demonstrating an optical vortex comb on a III–V integrated non-linear ring microresonator. The angular grating-dressed non-linear microring simultaneously emits spatiotemporal light springs consisting of 50 OAM modes, with each frequency of the microcomb carrying a distinct OAM value. We also experimentally generate optical pulses with time-varying OAM by carefully endowing the spatiotemporal light springs with a specific intermodal phase relation. We expect our work to favour the development of integrated non-linear and quantum photonics for exploring fundamental optical physics and advancing photonic quantum technology. Microring-based vortex combs with each comb line carrying a distinct orbital angular momentum generate light springs with time-varying orbital angular momenta. [ABSTRACT FROM AUTHOR]

Nonlinear optical signal processing (NOSP) has the potential to significantly improve the throughput, flexibility, and cost-efficiency of optical communication networks by exploiting the intrinsically ultrafast optical nonlinear wave mixing. It can support digital signal processing speeds of up to terabits per second, far exceeding the line rate of the electronic counterpart. In NOSP, high-intensity light fields are used to generate nonlinear optical responses, which can be used to process optical signals. Great efforts have been devoted to developing new materials and structures for NOSP. However, one of the challenges in implementing NOSP is the requirement of high-intensity light fields, which is difficult to generate and maintain. This has been a major roadblock to realize practical NOSP systems for high-speed, high-capacity optical communications. Here, we propose using a parity-time (PT) symmetric microresonator system to significantly enhance the light intensity and support high-speed operation by relieving the bandwidth-efficiency limit imposed on conventional single resonator systems. The design concept is the co-existence of a PT symmetry broken regime for a narrow-linewidth pump wave and near-exceptional point operation for broadband signal and idler waves. This enables us to achieve a new NOSP system with two orders of magnitude improvement in efficiency compared to a single resonator. With a highly nonlinear AlGaAs-on-Insulator platform, we demonstrate an NOSP at a data rate approaching 40 gigabits per second with a record low pump power of one milliwatt. These findings pave the way for the development of fully chip-scale NOSP devices with pump light sources integrated together, potentially leading to a wide range of applications in optical communication networks and classical or quantum computation. The combination of PT symmetry and NOSP may also open up opportunities for amplification, detection, and sensing, where response speed and efficiency are equally important. [ABSTRACT FROM AUTHOR]

We study canonical quantization of Jackiw-Teibelboim (JT) gravity coupled to a massless scalar field. We provide concrete expressions of matter SL(2, R) charges and the boundary matter operators in terms of the creation and annihilation operators in the scalar field. The matter charges are represented in the form of an oscillator (Jordon-Schwinger) realization of the SL(2, R) algebra. We also show how the gauge constraints are implemented classically, by matching explicitly classical solutions of Schwarzian dynamics with bulk solutions. We introduce n-point transition functions defined by insertions of boundary matter operators along the two-sided Lorentzian evolution, which may fully spell out the quantum dynamics in the presence of matter. For the Euclidean case, we proceed with a two-sided picture of the disk geometry and consider the two-sided 2-point correlation function where initial and final states are arranged by inserting matter operators in a specific way. For some simple initial states, we evaluate the correlation function perturbatively. We also discuss some basic features of the two-sided correlation functions with additional insertions of boundary matter operators along the two-sided evolution. [ABSTRACT FROM AUTHOR]

Today's optical communication systems are fast approaching their capacity limits in the conventional telecom bands. Opening up new wavelength bands is becoming an appealing solution to the capacity crunch. However, this ordinarily requires the development of optical transceivers for any new wavelength band, which is time-consuming and expensive. Here, we present an on-chip continuous spectral translation method that leverages existing commercial transceivers to unlock the vast and currently unused potential new wavelength bands. The spectral translators are continuous-wave laser pumped aluminum gallium arsenide on insulator (AlGaAsOI) nanowaveguides that provide a continuous conversion bandwidth over an octave. We demonstrate coherent transmission in the 2-μm band using well-developed conventional C-band transmitters and coherent receivers, as an example of the potential of the spectral translators that could also unlock communications at other wavelength bands. We demonstrate 318.25-Gbit s−1 Nyquist wavelength-division multiplexed coherent transmission over a 1.15-km hollow-core fibre using this approach. Our demonstration paves the way for transmitting, detecting, and processing signals at wavelength bands beyond the capability of today's devices. Continuous spectral translation could allow expansion of the bandwidth available for communication without having to develop transceivers for the new bands. Here, the authors demonstrate this using AlGaAsOI nanowaveguides as spectral translators between the mature telecom C band and the 2-μm wavelength band. [ABSTRACT FROM AUTHOR]

We explore the entanglement evolution of boundary intervals in eternal Janus black holes that can be embedded consistently into string theory in the low-energy limit. By studying the geodesics we show that there is a transition in the entanglement characteristic around the Page time, which manifests the unitarity of the evolution. We reproduce and reinterpret these bulk results from two different lower-dimensional perspectives: first as an interface CFT in the usual AdS/CFT correspondence and second as an effective gravity theory in one lower dimension coupled to a radiation background. In the limit where the number of interface degrees of freedom becomes large, we obtain an effective theory on appropriate branes that replace the deep interior region in the bulk, coined the shadow region. In this effective theory, we also identify the island of the radiation entanglement wedge and verify the newly proposed quantum extremization method. Our model clarifies that double holography with gravity in two higher dimensions can be realized in a concrete and consistent way and that the occurrence of islands is natural in one higher dimension. Furthermore, our model reveals that there can be a transitional behavior of the Page curve before the Page time, which is related to the emergence of new matter degrees of freedom on the branes. [ABSTRACT FROM AUTHOR]

We propose possible probes which could be used to demonstrate experimentally the existence of the bulk and the formation of a traversable wormhole purely in terms of boundary operations only. In the two-dimensional Einstein-dilaton gravity, the traversable wormhole is realized by turning on a double trace interaction which couples the two boundaries of the AdS2 black hole. Signals can propagate in the traversable wormhole through two different channels. The boundary channel is direct and instantaneous, while the bulk channel respects the bulk causality and takes a certain amount of time to complete signaling. In the latter case, we show that the signal frequency detected on the other side is highly modulated in general. The time delay as well as the frequency-modulation pattern could then be clear indications that the signal comes out through the bulk channel. We discuss the characteristics of the observed signal more explicitly for simple transitional configurations of the black hole from/to the eternal traversable wormhole. [ABSTRACT FROM AUTHOR]

Recently, N = 3 mass-deformed ABJM model with arbitrary mass-function depending on a spatial coordinate was constructed. In addition to the N = 3 case, we construct lower supersymmetric N = 1 and N = 2 inhomogeneously mass-deformed ABJM (ImABJM) models, which require three and two arbitrary mass-functions, respectively. We also construct general vacuum solutions of the N = 3 ImABJM model for any periodic mass-function. There are two classes of vacua, which are diagonal type and GRVV type according to reference value of mass-functions. We provide explicit examples of the vacuum solutions and discuss related operators. [ABSTRACT FROM AUTHOR]

We find general deformations of BTZ spacetime and identify the corresponding thermofield initial states of the dual CFT. We deform the geometry by introducing bulk fields dual to primary operators and find the back-reacted gravity solutions to the quadratic order of the deformation parameter. The dual thermofield initial states can be deformed by inserting arbitrary linear combination of operators at the mid-point of the Euclidean time evolution that appears in the construction of the thermofield initial states. The deformed geometries are dual to thermofield states without deforming the boundary Hamiltonians in the CFT side. We explicitly demonstrate that the AdS/CFT correspondence is not a linear correspondence in the sense that the linear structure of Hilbert space of the underlying CFT is realized nonlinearly in the gravity side. We also find that their Penrose diagrams are no longer a square but elongated horizontally due to deformation. These geometries describe a relaxation of generic initial perturbation of thermal system while fixing the total energy of the system. The coarse-grained entropy grows and the relaxation time scale is of order β/2π. We clarify that the gravity description involves coarse-graining inevitably missing some information of nonperturbative degrees. [ABSTRACT FROM AUTHOR]

Reflection amplitudes are defined as two-point functions of certain class of conformal field theories where primary fields are given by vertex operators with real couplings. Among these, we consider (Super-) Liouville theory and simply and non-simply laced Toda theories. In this paper we show how to compute the scaling functions of effective central charge for the models perturbed by some primary fields which maintains integrability. This new derivation of the scaling functions are compared with the results from conventional TBA approach and confirms our approach along with other non-perturbative results such as exact expressions of the on-shell masses in terms of the parameters in the action, exact free energies. Another important application of the reflection amplitudes is a computation of one-point functions for the integrable models. Introducing functional relations between the one-point functions in terms of the reflection amplitudes, we obtain explicit expressions for simply-laced and non-simply-laced affine Toda theories. These nonperturbative results are confirmed numerically by comparing the free energies from the scaling functions with exact expressions we obtain from the one-point functions. [ABSTRACT FROM AUTHOR]