Quantum Optical State Comparison Amplifier

Abstract

It is a fundamental principle of quantum theory that an unknown state cannot be copied or, as a consequence, an unknown optical signal cannot be amplified deterministically and perfectly. Here we describe a protocol that provides nondeterministic quantum optical amplification in the coherent state basis with high gain and high fidelity and which does not use quantum resources. The scheme is based on two mature quantum optical technologies: coherent state comparison and photon subtraction. The method compares favorably with all previous nondeterministic amplifiers in terms of fidelity and success probability

Experimental Implementation of a Quantum Optical State Comparison Amplifier

“…3) making high-quality transmission of quantum information at large data rates possible. For example, for the two-state set and \a\2 = 0.94, we obtain more than 26 k s -1 almost perfectly amplified states, corresponding to a measured success probability of 2.6% [22], For perfectly efficient detectors and no internal losses the maximum theoretical success probability at this mean photon number is 9.9%. The rate can be increased by reducing losses or increasing the pulse repetition frequency (PRF).…”

“…Here, we demonstrate experimentally our protocol [22] that, using coherent light sources, linear optical compo nents, and commercial photodetectors, can amplify coher ent states of any experimentally reasonable amplitude chosen from a limited set, using the established techniques of nondemolition comparison [23] and photon subtraction [24] . The operation of the experiment is shown in Fig.…”

From retrodiction to Bayesian quantum imaging

“…It has been valuable, however, in simplifying calculations and, more importantly, suggesting possibilities and ideas that are not readily apparent in the more familiar predictive approach. Striking examples include a novel class of generalised measurements [24,25], quantum information processing in the past [26] and the quantum scissors device [27,28] and the field of noiseless amplification that it led to [29][30][31][32][33]. In the context of quantum imaging, it has provided a novel analysis of entangled photon ghost imaging [34] including a justification for the Klyshko interpretation of the phenomenon [35].…”

Models of reduced-noise, probabilistic linear amplifiers

“…Ralph and Lund [6] and, independently, Fiurášek [7] (in the context of cloning) proposed an intriguing idea that suggested it might be possible to build an amplifier that subtracts noise! This proposal continues to generate interest from the community [8][9][10][11][12][13][14][15][16][17], with potential applications including quantum key distribution [18][19][20] and the distillation of quantum correlations [12]. Specifically, the proposed amplifier with amplitude gain g > 1 takes an input coherent state |α to a "target" coherent state |gα with (success) probability p and fails with probability 1 − p .…”