A Method to Compute the Schrieffer–Wolff Generator for Analysis of Quantum Memory

Microwave quantum illumination with entangled pairs of microwave signal and optical idler modes can achieve sub‐optimal performance with joint measurement of the signal and idler modes. Here, a testbed for microwave quantum illumination is proposed with an optical memory simulated with a delay line in the idler mode. It provides the amount of input two‐mode squeezing necessary to compensate for the loss of optical memory while maintaining a quantum advantage over a coherent state. When the memory is lossy, the input two‐mode squeezing has to be higher through high cooperativity in the optical mode. Under the testbed, a single‐mode phase conjugate receiver is proposed consisting of a low‐reflectivity beam splitter, an electro‐optomechanical phase conjugator, and a photon number‐resolving detector. The performance of the newly proposed receiver approaches the sub‐optimal quantum advantage of 3 dB. Furthermore, the receiver achieves the quantum advantage even with an on‐off detection while being robust against the loss of the memory.

In quantum illumination, the signal mode of light, entangled with an idler mode, is dispatched towards a suspected object bathed in thermal noise and the returning mode, along with the stored idler mode, is measured to determine the presence or absence of the object. In this process, entanglement is destroyed but its benefits in the form of classical correlations and enlarged Hilbert space survive. Here, we propose the use of probe state hyperentangled in two degrees of freedom - polarization and frequency, to achieve a significant 12dB performance improvement in error probability exponent over the best known quantum illumination procedure in the low noise regime. We present a simple receiver model using four optical parametric amplifiers (OPA) that exploits hyperentanglement in the probe state to match the performance of the feed-forward sum-frequency generator (FF-SFG) receiver in the high noise regime. By replacing each OPA in the proposed model with a FF-SFG receiver, further 3dB improvement in the performance of a lone FF-SFG receiver can be seen.

This work presents a semiconductor vertical triple microcavity system consisting of a MBE grown structure, made of three AlGaAs/GaAs lambda-microcavities, including single InGaAs quantum wells. The work investigated an experimental configuration expected to be optimal for generating correlated polariton modes: the pump is at 0deg, resonant with the second branch, and the signal and idler modes are at the same energy and opposite angles on the low energy branch. With this excitation geometry, a high symmetry between signal and idler modes is achieved (same photon content and same linewidth) which ensure maximal correlations. Moreover, the fact that the pump is at normal incidence allows eliminating spurious uncorrelated background noise contributions coming from the resonant Rayleigh scattering of the pump mode. Results show that in the strong light-matter coupling regime (temperature of 4 K, pump excitation 20 mW), the noise spectrum of the difference reveals 5% squeezing, demonstrating the first generation of quantum correlated polariton modes.

The polariton dynamics in a microcavity in the parametric oscillator mode is studied when two pump polaritons turn into polaritons of signal and idler modes and vice versa. The pumping is performed by two laser pulses with close frequencies. Analytical solutions to a system of nonlinear differential equations are obtained. Periodic and aperiodic regimes of transformation of a pair of pump polaritons into polaritons of signal and idler modes, as well as the quiescent mode of the system, are obtained.

A moving pellicle superconducting mirror, which is driven by radiation pressure on its one side and the Coulomb force on its other side, can become a parametric oscillator that can generate microwaves when placed within a high-Q superconducting Fabry–Perot resonator system. A paraxial-wave analysis shows that the fundamental resonator eigenmode needed for parametric oscillation is the TM011 mode. A double Fabry–Perot structure is introduced to resonate the pump and idler modes, but reject the parasitic anti-Stokes mode. The threshold for oscillation is estimated based on the radiation–pressure coupling of the pump to the signal and idler modes and indicates that the experiment is feasible to perform.

We started to research quantum illumination radar and quantum imaging by utilizing high quality continuous-wave two-mode squeezed light source as a quantum entanglement resource. Two-mode squeezed light is a macroscopic quantum entangled state of the electro-magnetic field and shows strong correlation between quadrature phase amplitudes of each optical field. One of the most effective methods to generate two-mode squeezed light is combining two independent single-mode squeezed lights by using a beam splitter with relative phase of 90 degrees between each optical field. As a first stage of our work we are developing two-mode squeezed light source for exploring the possibility of quantum illumination radar and quantum imaging. In this article we introduce current development of experimental investigation of single-mode squeezed light. We utilize a sub-threshold optical parametric oscillator with bow-tie configuration which includes a periodically-polled potassium titanyl phosphate crystal as a nonlinear optical medium. We observed the noise level of squeezed quadrature −3.08±0.13 dB and anti-squeezed quadrature at 9.29±0.13 dB, respectively. We also demonstrated the remote tuning of squeezing level of the light source which leads to the technology for tuning the quantum entanglement in order to adapt to the actual environmental condition.

Single-photon sources of high efficiency are of great interest because they are the key elements in many prospective quantum technologies and applications. Based on our previous work, here we demonstrate a high-quality tunable microwave single-photon source based on transmon qubit with intrinsic emission efficiency more than 99%. To further confirm the single-photon property of the source, we study the single-photon interference in a Hanbury-Brown-Twiss (HBT) type setup and measure the correlation functions of the emission field using linear detectors with GPU-enhanced signal processing technique. The antibunching in second-order correlation function is clearly observed. The theoretical calculations agree well with the experimental results. Such a high-quality single-photon source may be used as a building block for quantum communication, simulation and information processing in microwave regime.

Feasible distribution of quantum entanglement over long distances remains a fundamental step towards quantum secure communication and quantum network implementations. Quantum repeater nodes based on quantum memories promise to overcome exponential signal decay inherent to optical implementations of quantum communication. While performance of current quantum memories hinders their practical application, multimode solutions with multiplexing can offer tremendous increase in entanglement distribution rates. We propose to use a wavevector-multiplexed atomic quantum memory (WV-MUX-QM) as a fundamental block of a multiplexed quantum repeater architecture. We show the WV-MUX-QM platform to provide quasi-deterministic entanglement generation over extended distances, mitigating the fundamental issue of optical loss even with currently available quantum memory devices, and exceeding performance of repeaterless solutions as well as other repeater-based protocols such as temporal multiplexing. We establish the entangled-bit (ebit) rate per number of employed nodes as a practical figure of merit reflecting the cost-efficiency of larger inter-node distances.

The number-quadrature minimum-uncertainty states after rotation and displacement emerge in the parametric down-conversion followed by photon number measurement in the idler mode when the coherent state inputs. Again, the state generated in the signal mode by the reduction is described by the principally measurable quantum-statistical tools.

By the birth of Quantum Physics, many new areas were opened for research and development in the world of science and technology. One such field is Quantum Computing and Communication where there is room for all that was once a dream in the field of computing and communication. Ultra high speed, immunity to eavesdropping, security, and name it and it may be possible. This paper gives a brief review of what is happening in the field of quantum computing and communication. We try to give an idea on polarization, quantum entanglement and their use in quantum communication and also briefly explain quantum communication networks, teleportation over optic fiber cables, quantum cryptography, quantum based satellite communication and quantum memory.

Chapter 7 - Quantum of radar theory

The exposition of the formalisms of the quantum optical phase has been provided commencing from the quantum mechanics of a massive particle. The clockwise and counterclockwise components of the planar motion are shown to correspond to the signal and idler modes in the heterodyne detection scheme. The appropriate ideal phase proposal has been embodied in this scheme.

In this paper we investigate the single-mode properties (Wigner function, photon-number distribution and quadrature squeezing) of a dissipative parametric amplifier when the signal and idler modes are initially prepared in the Schrodinger-cat states. We show that there are two sources producing decoherence in the system, which are spontaneous pump photon decay and interaction with the environment. For the latter case, the system collapses to both statistical mixture states as well as thermal states governed by the interaction parameters.

We present results of a bright polarization-entangled photon source operating at 1552 nm via type-II collinear degenerate spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We report a conservative inferred pair generation rate of 123,000 pairs/s/mW into collection modes. Minimization of spectral and spatial entanglement was achieved by group velocity matching the pump, signal, and idler modes and through properly focusing the pump beam. By utilizing a pair of calcite beam displacers, we are able to overlap photons from adjacent down-conversion processes to obtain polarization-entanglement visibility of 94.7+/-1.1% with accidentals subtracted.

Nonlinear optical processes are an essential tool in modern optics, with a broad spectrum of applications, including signal processing, frequency conversion, spectroscopy and quantum optics. Ordinary parametric devices nevertheless still suffer from relatively low gains and wide spectral emission. Here we demonstrate a unique configuration for phase-matching multiple nonlinear processes in a monolithic 2D nonlinear photonic crystal, resulting in the coherent parametric emission of four signal and idler modes, featuring an exponential gain enhancement equal to the Golden Ratio. The results indicate a new route towards compact high-brightness and coherent sources for multi-photon generation, manipulation and entanglement, overcoming limitations of conventional parametric devices.