Quenches in isolated quantum systems are currently a subject of intense study. Here, we consider quantum few-mode systems that are integrable in their classical mean-field limit and become dynamically unstable after a quench of a system parameter. Specifically, we study a Bose-Einstein condensate (BEC) in a double-well potential and an antiferromagnetic spinor BEC constrained to a single spatial mode. We study the time dynamics after the quench within the truncated Wigner approximation (TWA), focus on the role of motion near separatrices, and find that system relaxes to a steady state due to phase-space mixing. Using the action-angle formalism and a pendulum as an illustration, we derive general analytical expressions for the time evolution of expectation values of observables and their long-time limits. We find that the deviation of the long-time expectation value from its classical value scales as $O(1/lnN)$ , where $N$ is the number of atoms in the condensate. Furthermore, the relaxation of an observable to its steady-state value is a damped oscillation. The damping is Gaussian in time with a time scale of $O[{(lnN)}^{2}]$ . We also give the quantitative dependence of the steady-state value and the damping time on the system parameters. Our results are confirmed with numerical TWA simulations.Quenches in isolated quantum systems are currently a subject of intense study. Here, we consider quantum few-mode systems that are integrable in their classical mean-field limit and become dynamically unstable after a quench of a system parameter. Specifically, we study a Bose-Einstein condensate (BEC) in a double-well potential and an antiferromagnetic spinor BEC constrained to a single spatial mode. We study the time dynamics after the quench within the truncated Wigner approximation (TWA), focus on the role of motion near separatrices, and find that system relaxes to a steady state due to phase-space mixing. Using the action-angle formalism and a pendulum as an illustration, we derive general analytical expressions for the time evolution of expectation values of observables and their long-time limits. We find that the deviation of the long-time expectation value from its classical value scales as $O(1/lnN)$, where $N$ is the number of atoms in the condensate. Furthermore, the relaxation of an observable to its steady-state value is a damped oscillation. The damping is Gaussian in time with a time scale of $O[{(lnN)}^{2}]$. We also give the quantitative dependence of the steady-state value and the damping time on the system parameters. Our results are confirmed with numerical TWA simulations.

arXiv:1705.01702Physical Review AJul 5, 201713 citations

Optimized entangled photon pair generation via intermodal four-wave mixing in a telecommunication-length few-mode fiber

Seyedehnajmeh Montazeri, Mina Esmaeelpour

We report our recent progress in generating and verifying entangled photon pairs in a telecommunication-length few-mode fiber using spontaneous four-wave mixing in a non-degenerate pump configuration. We demonstrate through seeding the desired four-wave mixing effect for pair production in the presence of a strong mode-coupling when using integrated mode multiplexers known as photonic lanterns. The mode content and phase-matching requirements were validated through computations and experiments. We discuss the challenges and requirements for phase matching and photon visibility without modifying the fiber structure. This work represents our first steps toward an efficient tunable source of entangled photons for space division multiplexing applications.We report our recent progress in generating and verifying entangled photon pairs in a telecommunication-length few-mode fiber using spontaneous four-wave mixing in a non-degenerate pump configuration. We demonstrate through seeding the desired four-wave mixing effect for pair production in the presence of a strong mode-coupling when using integrated mode multiplexers known as photonic lanterns. The mode content and phase-matching requirements were validated through computations and experiments. We discuss the challenges and requirements for phase matching and photon visibility without modifying the fiber structure. This work represents our first steps toward an efficient tunable source of entangled photons for space division multiplexing applications.

Quantum Computing, Communication, and SimulationMar 12, 20240 citations

Integrable Many-Particle Systems

V. I. Inozemtsev

WORLD SCIENTIFIC (EUROPE) eBooksSep 27, 20221 citation

Entangled photon pair generation via spontaneous intermodal four-wave mixing in a 25km few-mode fiber

Seyedehnajmeh Montazeri, Mina Esmaeelpour

High degrees of security have been achieved in quantum communication over fiber using entangled photons. For communications applications, it is crucial to produce high-yield entangled photon pairs (EPPs) with the capacity to transmit them over telecommunication-length fiber distances and the ability to integrate and transmit them over existing classical communication systems. Since spatial division multiplexing (SDM) is currently being demonstrated to replace single-mode communication systems, it only makes sense to demonstrate the generation and transferring EPPs in various fiber modes suitable for generation and transmission in SDM fibers. We experimentally demonstrate EPP formation in a 25-km-long graded-index few-mode fiber (three modes) via the intermodal spontaneous four-wave mixing (SFWM) effect. Mode profile and phase matching condition have been confirmed through experiments.High degrees of security have been achieved in quantum communication over fiber using entangled photons. For communications applications, it is crucial to produce high-yield entangled photon pairs (EPPs) with the capacity to transmit them over telecommunication-length fiber distances and the ability to integrate and transmit them over existing classical communication systems. Since spatial division multiplexing (SDM) is currently being demonstrated to replace single-mode communication systems, it only makes sense to demonstrate the generation and transferring EPPs in various fiber modes suitable for generation and transmission in SDM fibers. We experimentally demonstrate EPP formation in a 25-km-long graded-index few-mode fiber (three modes) via the intermodal spontaneous four-wave mixing (SFWM) effect. Mode profile and phase matching condition have been confirmed through experiments.

Quantum Computing, Communication, and SimulationMar 8, 20231 citation

Relaxations in few-body systems

Yasushi Kondo

Bulletin of the American Physical SocietyMar 15, 20170 citations

O(1/lnN)

, where

N

is the number of atoms in the condensate. Furthermore, the relaxation of an observable to its steady-state value is a damped oscillation. The damping is Gaussian in time with a time scale of

O[{(lnN)}^{2}]

. We also give the quantitative dependence of the steady-state value and the damping time on the system parameters. Our results are confirmed with numerical TWA simulations.