Quantum-enhanced noise radar

Abstract

We propose a novel protocol for quantum illumination: a quantum-enhanced noise radar. A two-mode squeezed state, which exhibits continuous-variable entanglement between so-called signal and idler beams, is used as input to the radar system. Compared to existing proposals for quantum illumination, our protocol does not require joint measurement of the signal and idler beams. This greatly enhances the practicality of the system by, for instance, eliminating the need for a quantum memory to store the idler. We perform a proof-of-principle experiment in the microwave regime, directly comparing the performance of a two-mode squeezed source to an ideal classical noise source that saturates the classical bound for correlation. We find that, even in the presence of significant added noise and loss, the quantum source outperforms the classical source by as much as an order of magnitude.Quantum illumination has recently gained attention as a possible avenue to improve the sensitivity of radar and other target detection technologies. 1,2 The approach takes advantage of strong signal correlations that can be created in electromagnetic beams using quantum processes. These quantum correlations, a form of entanglement, can be stronger than anything allowed by classical physics giving a "quantum advantage" to the detection process. A number of proposals exist to use these correlations in a wide range of quantum sensing applications with the goal of making precision measurements beyond the standard quantum limit. 3,4 Most of these applications require that the entire sensor system be low-noise and have negligible loss in order to maintain entanglement. Notably, quantum illumination seems to be very robust to the presence of background noise and loss, suggesting that it may have broader practical applications.In this Letter, we present measurements demonstrating the potential of a novel quantum illumination protocol that implements a form of noise radar. Noise radar has been studied in the classical regime because of, among other reasons, the inherent difficulty in detecting the noisy probe beam against the ambient thermal background noise. 5,6 As discussed below, our protocol relaxes a challenging requirement of existing protocols, namely, joint measurement. This greatly increases the practicality of our scheme compared to others. In a proof-ofprinciple experiment, we use the protocol to demonstrate a quantum enhancement in the detected signal-to-noise ratio of an order of magnitude when comparing the performance of an entangled-photon source to an ideal classical noise source that saturates the classical bound for correlation.At the heart of quantum illumination (QI) is a nonlinear quantum process known as parametric downconversion (PDC). In PDC, a strong pump beam with a high frequency, f p , is incident on a nonlinear medium, resulting in the production of two lower frequency beams, commonly referred to as the signal and idler, such that the frequencies of the produced beams, f s and f i , satisfy the relation f p = f s + f i ...

Imaging through noise with quantum illumination

“…The protocol has also been proposed to be useful for detecting the presence of a target object embedded within a noisy background, despite environmental perturbations and losses destroying the initial entanglement [5,6,7].In 2013, Lopaeva et al performed an experimental demonstration of the quantum illumination principle, to determine the presence or absence of a semi-transparent object, by exploiting intensity correlations of a quantum origin in the presence of thermal light [8]. Additionally, a quantum illumination protocol has been experimentally demonstrated in the microwave domain [9] and a further demonstration in which joint detection of the signal and idler is not required [10]. However, these previous demonstrations were restricted 1 to simply detecting the presence or absence of a target, rather than performing any form of spatially resolved imaging.…”

Quantum Two-Mode Squeezing Radar and Noise Radar: Correlation Coefficients for Target Detection

“…Quantum illumination radars [1]- [4], which are based on a phenomenon called entanglement, are a particularly well-studied class of quantum radars. An experimental implementation of a quantum two-mode squeezing (QTMS) radar, a variant of quantum illumination radar, was recently demonstrated [5]- [7]. Although it is not a full quantum radar (it uses amplifiers which break the entanglement), it demonstrates all the necessary ingredients of an entanglement-based radar, including the generation of an entangled signal and the transmission of microwaves through free space.…”

“…[8]) in that they rely on the correlation between two noise signals for target detection. In fact, the name adopted for QTMS radar in [5] was quantum-enhanced noise radar. One of the noise signals is transmitted toward a target, while the other is retained within the radar system.…”

Quantum illumination assistant with error-correcting codes

“…The properties of quantum states have disclosed the possibility of realizing this task beyond classical limits [1][2][3]. One of the major applications to enhance the ability of target recognition is quantum illumination [4][5][6][7][8][9], which is the most known protocol for bosonic quantum sensing [10]. Quantum illumination provides us with a potential platform to detect the low-reflectivity object embedded in a bright environment, and it is more efficiently than the way by using classical resources [5,11,12].…”