New Journal of Physics

Quantum squeezing and entanglement from a two-mode phase-sensitive amplifier via four-wave mixing in rubidium vapor

Yami Fang, Jietai Jing

Published Feb 10, 2015• 70 citations

Abstract

Phase-sensitive amplifiers (PSAs) have been widely studied in fiber amplifiers, with remarkable recent advances. They have also been implemented in an SU(1,1) interferometer. In this paper, we study an experimental scheme for the implementation of a two-mode PSA based on a four-wave mixing process in rubidium vapor. With the process seeded by coherent probe and conjugate beams, quantum correlation including intensity difference/sum squeezing and quadrature entanglement between the output probe and conjugate fields are theoretically analyzed. Compared to previous related research, several new and interesting results are reported here. The maximal degree of intensity difference squeezing can be enhanced by nearly 3 dB compared to a phase-insensitive amplifier with the same gain. It is also possible to generate intensity sum squeezing between the probe and conjugate fields by choosing the specific phase of the input beams. Moreover, quadrature entanglement between the probe and conjugate beams, which can be manipulated by the phase of the input beams, is predicted. Our scheme may find a variety of applications in quantum metrology and quantum information processing owing to its ability of quantum squeezing and entanglement manipulation.

DOI: 10.1088/1367-2630/17/2/023027

Related papers

Interference-Induced Quantum Squeezing Enhancement in a Two-beam Phase-Sensitive Amplifier

Shengshuai Liu, Yanbo Lou, Jietai Jing

We experimentally demonstrate a method for realizing quantum squeezing enhancement which is induced by the interference in a two-beam phase-sensitive amplifier (PSA) based on a four-wave mixing process. Compared to the normal phase-insensitive amplifier with an intensity-difference squeezing (IDS) of 8.97±0.24 dB or 8.76±0.26 dB, the IDS of our two-beam PSA is enhanced to 10.13±0.21 dB under the same experimental situation. Furthermore, we study how various parameters influence the quantum squeezing enhancement of the PSA. These results clearly show that the physical mechanism inducing the IDS enhancement of the two-beam PSA is its intrinsic interference nature. Our results may find potential applications in improving the fidelity of quantum information processing and the precision of quantum metrology.

Physical Review LettersSep 9, 201991 citations

Phase-sensitive cascaded four-wave-mixing processes for generating three quantum correlated beams

Li Wang, Hailong Wang, Sijin Li +2 more

Theoretical studies and experimental implementations of quantum correlation are the important contents of continuous variables quantum optics and quantum information science. There are various systems for the study of quantum correlation. Here, we study an experimental scheme for generating three quantum correlated beams based on phase-sensitive cascaded four-wave-mixing (FWM) processes in rubidium vapor. Quantum correlation including intensity difference or sum squeezing, two other combinatorial squeezing, and quantum entanglement among the three output light fields are theoretically analyzed in this paper. Also, the comparison of the quantum correlations have been made between the phase-sensitive cascaded FWM processes and the phase-insensitive cascaded FWM processes. By changing the phases and intensities of the input beams, it is interesting to find that the maximum degrees of various combinatorial squeezing are equal when the two FWM processes share a common intensity gain. When the common intensity gain of the two FWM processes changes, the maximum degrees of different combinatorial squeezing will be synchronously controlled. At last we discuss the genuine tripartite entanglement and steering in our phase-sensitive cascaded scheme, and compare them with the cases of the phase-insensitive cascaded scheme.

Physical Review AJan 5, 201714 citations

Experimental enhancement of six-beam quantum squeezing by phase-sensitive cascaded four-wave mixing processes

Jiabin Wang, Yanbo Lou, Shengshuai Liu +1 more

We experimentally realize the enhancement of six-beam quantum squeezing by utilizing a six-beam phase-sensitive amplifier (PSA) based on cascaded four-wave mixing processes. Compared to the intensity-difference squeezing (IDS) of about 5.03 or 5.09 dB generated by a six-beam phase-insensitive amplifier (PIA), the six-beam IDS generated by the six-beam PSA is enhanced to about 6.64 dB. The intrinsic interference of six-beam PSA induces this enhancement. In addition, we investigate the dependence of IDS generated by the six-beam PSA and PIAs on the powers of two pump beams. The results show that the IDS of six-beam PSA is always better than that of six-beam PIAs. Our scheme may find potential applications in high-precision multi-parameter quantum metrology.

Optics ExpressJul 4, 20245 citations

Phase manipulated two-mode entangled state from a phase-sensitive amplifier

Shengshuai Liu, Yanbo Lou, Jietai Jing

The phase manipulation of the two-mode entangled state, which can flexibly control the combination of quadrature components on demand, is important for continuous variable (CV) quantum information and quantum metrology. Here, we experimentally demonstrate the phase manipulation of entangled state by using a phase-sensitive amplifier (PSA) based on four-wave mixing (FWM) process. The entanglement with different phase space squeezing orientations can be generated by directly changing the phase of the PSA. Our scheme is concise and can be expanded to generate multi-parties entangled states on demand. Our results here pave the way to realize a phase-coded quantum key distribution protocol and squeezing-enhanced Raman spectroscopy.

Optics ExpressOct 29, 20215 citations

Squeezed Light and Entangled Images from Four-Wave-Mixing in Hot Rubidium Vapor

Raphael C. Pooser, Vincent Boyer, Alberto M. Marino +1 more

Entangled multi-spatial-mode fields have interesting applications in quantum information, such as parallel quantum information protocols, quantum computing, and quantum imaging. We study the use of a nondegenerate four-wave mixing process in rubidium vapor at 795 nm to demonstrate generation of quantum-entangled images. Owing to the lack of an optical resonator cavity, the four-wave mixing scheme generates inherently multi-spatialmode output fields. We have verified the presence of entanglement between the multi-mode beams by analyzing the amplitude difference and the phase sum noise using a dual homodyne detection scheme, measuring more than 4 dB of squeezing in both cases. This paper will discuss the quantum properties of amplifiers based on four-wave-mixing, along with the multi mode properties of such devices.

Nov 21, 20122 citations

Optical properties of a quantum-noise-limited phase-sensitive amplifier

Tian Li

This dissertation is a summary of investigations on the optical properties of a quantum-noise-limited phase-sensitive amplifier (PSA). The PSA is implemented using four-wave mixing in hot Rb 85 vapor based on a double-Lambda atomic scheme. We experimentally demonstrate the ability of a PSA to pre-amplify quantum correlations in twin light beams produced by a phase-insensitive amplifier (PIA) before degradation due to loss and detector inefficiency. By including a PSA before loss, one is able to preserve the correlations as well as the two-mode squeezing level. We compare the results to simulations employing a simple quantum-mechanical model and find a good agreement. We have demonstrated that the cross-correlation between the two modes of a bipartite entangled state can be advanced by propagation through a PIA acting as a fast-light medium. The extra noise added by the PIA has been speculated to be the mechanism that limits the advance of entanglement, preventing the mutual information from traveling superluminally. As an extension of this phase-insensitive, gain-assisted, anomalous dispersion investigation, we explore the advance and delay of information transmitted through the PSA. We start with a two-mode squeezed state created by the PIA and measure the mutual information shared by the correlated quadratures. We then pass one of these two modes through a PSA and investigate the shift of the mutual information as a function of the PSA phase. In the case of a PSA, it is well known that no extra noise will be added to the quadrature with the correct input phase (e.g., the quadrature with the maximal amplification or the maximal deamplification). We find that there is no dispersion-like behavior at these two phases, however, the peak of mutual information could either be delayed or advanced at any other phase. We also observe an almost identical behavior when we input an amplitude modulated signal to the PSA. We are able to explain the physics of this ``fast-and-slow-light'' type of behavior utilizing a model assuming imbalanced gain on the positive and negative side bands. We obtain a good agreement between the experimental results and the theoretical simulations.

Jan 1, 20170 citations