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IEEE Access

On Entanglement Assisted Classical Optical Communication With Transmitter Side Optical Phase-Conjugation

Ivan B. Djordjević

Published Jan 1, 2021• 9 citations
Publisher

Abstract

Entanglement assisted (EA) communication has been advocated by numerous authors as a potential alternative to classical communications, in particular in noisy and low-brightness regime. In this paper, we propose an EA scheme employing the optical phase-conjugation (OPC) on transmitter side. We show that the proposed EA communication system, with the transmitter side OPC, significantly outperforms its classical counterpart in low-brightness and highly noisy regime, while employing a classical coherent detection scheme for two-dimensional demodulation. Moreover, the capacity of the proposed EA scheme is significantly higher than EA repetition-BPSK, homodyne, heterodyne, and Holevo capacities. Finally, the proposed EA scheme outperforms the corresponding EA scheme with OPC placed on a receiver side.

DOI
10.1109/access.2021.3137670

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Entanglement assisted (EA) communication has been advocated by numerous authors as a potential alternative to classical communications, in particular in noisy and low-brightness regime. In this paper, we propose an EA scheme employing the optical phase-conjugation (OPC) on transmitter side. We show that the proposed EA communication system, with the transmitter side OPC, significantly outperforms its classical counterpart in low-brightness and highly noisy regime, while employing a classical coherent detection scheme for two-dimensional demodulation. Moreover, the capacity of the proposed EA scheme is significantly higher than EA repetition-BPSK, homodyne, heterodyne, and Holevo capacities. Finally, the proposed EA scheme outperforms the corresponding EA scheme with OPC placed on a receiver side.
Entanglement is a unique quantum information processing feature. With the help of entanglement we can build quantum sensors whose sensitivity is better than that of classical sensors. In this paper we are concerned with the entanglement assisted (EA) bistatic quantum radar applications. By employing the optical phase conjugation (OPC) on transmitter side and classical coherent detection on receiver side we show that the detection probability of the proposed EA target detection scheme is significantly better than that of corresponding classical and coherent states-based quantum detection schemes. The proposed EA target detection scheme is evaluated by modelling the radar return channel as the lossy and noisy Bosonic channel and assuming imperfect distribution of entanglement over the idler channel.
Entanglement assisted (EA) communication represents an interesting alternative to classical communication, in particular in low-brightness and highly noisy regime when it outperforms significantly corresponding classical counterpart in terms of the channel capacity. Even though that the EA capacity is known for decades the optimum quantum receiver has not been determined yet. In this paper, we propose several low-complexity quantum receivers outperforming recently proposed receivers employing the optical parametric amplifier as a basic building block. We demonstrate by simulations that the capacity of the proposed EA schemes, employing Gaussian modulation and the proposed low-complexity joint receivers, can significantly outperform both the Holevo capacity and classical homodyne and heterodyne channel capacities.
In this invited paper, we describe our entanglement assisted (EA) MIMO quantum radar technique with multiple entangled transmitters and coherent detection-based receivers. This scheme exploits the phase sensitive quantum correlation on the receivers’ sides to improve the receiver sensitivity. To increase overall signal-to-noise ratio, we use the spatial MIMO concept. To reduce the system cost and complexity, the optical phase conjugation (OPC) on signal photons is performed on a transmitter side, so that commercially available classical, balanced coherent detectors can be used on receiver side instead of traditional OPC-based EA receivers.
In entanglement assisted communications and sensing the optical phase-conjugation (OPC), required before homodyne detection takes place, is typically performed on signal photons on receive side. Unfortunately, in turbulent free-space optical channels, the signal photons can be scattered or absorbed by the channel, and if they reach the receive side they are very weak. Here we propose an entanglement assisted radar technique in which the OPC is performed on bright idler photons instead. By performing the OPC on idler photons on transmit side, while employing adaptive optics and classical homodyne detection on receive side, we experimentally demonstrate that the target detection probability of the proposed entanglement assisted radar over turbulent free-space optical channel is significantly better than that of corresponding classical detection scheme.
With the help of entanglement, we can build quantum sensors with sensitivity better than that of classical sensors. In this paper we propose an entanglement assisted (EA) joint monostatic-bistatic quantum radar scheme, which significantly outperforms corresponding conventional radars. The proposed joint monostatic-bistatic quantum radar is composed of two radars, one having both wideband entangled source and EA detector, and the second one with only an EA detector. The optical phase conjugation (OPC) is applied on the transmitter side, while classical coherent detection schemes are applied in both receivers. The joint monostatic-bistatic integrated EA transmitter is proposed suitable for implementation in LiNbO3 technology. The detection probability of the proposed EA joint target detection scheme outperforms significantly corresponding classical, coherent states-based quantum detection, and EA monostatic detection schemes. The proposed EA joint target detection scheme is evaluated by modelling the direct radar return and forward scattering channels as both lossy and noisy Bosonic channels, and assuming that the distribution of entanglement over idler channels is not perfect.
Optical communications over terrestrial free-space optical (FSO) channels are affected by various effects including diffraction, absorption, scattering, and turbulence effects. In several recent papers we have shown that entanglement assisted (EA) communication systems significantly outperform corresponding classical counterparts in strong turbulence regime. In traditional EA communications the phase-conjugation, required before the homodyne detection takes place, is performed on signal photons. However, given that many photons get lost due to diffraction, scattering, absorption, and turbulence effects, it is extremely difficult to perform the phase-conjugation on received signal photons when average number of received photons is smaller than 1. To solve this problem, we recently have proposed to perform phase-conjugation on bright idler photons instead. To operate the EA communication system over turbulent FSO links it is required to generate many bright entangled photons so that signal photons can survive beyond strong turbulence regime. To solve this problem, we have proposed to properly design periodically poled lithium niobate waveguides so that we can use telecom available lasers operated in S-, C-, and L-bands as the pump lasers instead of high-cost 780 nm pump lasers. In this invited paper, we will review our recent activities in EA communion studies over terrestrial FSO links and present recent experimental results demonstrating that EA communication systems performing the phase-conjugation on idler photons significantly outperforms both classical counterpart and the EA communications with phase-conjugated receiver in strong turbulence regime.