In this paper, we propose a novel quantum backscatter communications (QBC) protocol, inspired by the quantum illumination (QI) concept. In the QBC paradigm, the transmitter generates entangled photon pair. The signal photon is transmitted and the idler photon is kept at the receiver. The tag antenna communicates by performing the pulse amplitude modulation (PAM), binary phase shift keying (BPSK) or quadratic phase shift keying (QPSK) on the signal impinging at the antenna. Using the sum-frequency-generation receiver, our QBC protocol achieves a 6 dB error exponent gain for PAM and BPSK, and 3 dB gain for QPSK over its classical counterpart. Finally, we discuss the QI-enhanced secure backscatter communication.

Backscattered signals are always obscured by the unavoidable channel noise. However, by exploiting quantum physics recent protocols had been developed to enhance the probability of detecting backscattered signals in a very noisy environment [1], [2]. In this paper we propose a new detection scheme that is simpler in nature than the sum frequency receiver that was proposed for the quantum illumination protocol [3]. Signals are generated using spontaneous parametric down conversion (SPDC) and are transmitted via the simple modulation technique of on-off keying (OOK), while the receiver design will rely upon the purely non-classical Hong-Ou-Mandel (HOM) effect.

The recent advances in the field of microwave superconducting circuits open the way for a multitude of engineering applications that revolutionize the field of classical communications. To exploit this new technology, we propose a novel microwave quantum-enhanced backscattering system based on the laws of quantum physics. Both the transmitter and the receiver are quantum mechanical in nature and are accommodated at the infrastructure side, while the backscattering device is classical. The advocated system breaks the performance barrier of the classical backscattering systems and approaches the ultimate attainable receiver sensitivity. Finally, our quantum solution outperforms the classical solutions in terms of its level of security.

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Quantum sensing based on entangled photon pairs is gradually establishing itself as a cornerstone in modern communication networks. The unrivalled capability of quantum sensing techniques in distilling signals plagued by noise, renders them suitable for deployment in backscatter communication networks. Several attempts have been made recently to utilize pairs of entangled signal-idler photons, to enhance the sensitivity of photo-detection in backscatter networks. However, these efforts have always assumed the lossless retention of the idler mode, which is a challenging task from a practical perspective. In this study we examine the extent to which quantum correlations remain after retaining the idler mode in a lossy memory element, while the signal photon propagates through a lossy thermal channel as usual. We also examine briefly two different detection methods, and estimate the received signal-to-noise ratio for them both. This new proposed model is one step further towards realizing quantum backscatter communication.