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Covariance matrix of the two-mode state. (a) The covariance matrix calculated from the single squeezer model parameter extracted by joint fitting of measured variances. (b) The 10 independent elements of the covariance matrix are shown for the same data as (a).
Source publication
By combining a squeezed propagating microwave field and an unsqueezed vacuum
field on a hybrid (microwave beam-splitter), we generate entanglement between
the two output modes. We verify that we have generated entangled states by
making independent and efficient single-quadrature measurements of the two
output modes. We observe the entanglement wit...
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... where we have introduced the parameter d P CR = √ MN 1 /σ 1 = 2 M κN S (N S + 1)/(N B + 1)(2N S + 1), and the new threshold parametrization as ln η = (s − 1/2)d 2 P CR . The corresponding ROC curves obtained from Eqs. (10)- (11) and Eqs. (12)- (13) and shown in Fig. 12 are practically indistinguishable in the considered regime. ...
... The full blue curve refers to QI with PCR detection: Eqs. (10)-(11) and Eqs. (12)-(13) provide indistinguishable curves for the chosen parameters, N S = 0.05, N B = 100, κ = 0.01, M = 1.5 × 10 7 . ...
p>In this article, the current status of a novel mi- crowave quantum radar (MQR) based on quantum illumination (QI) protocol using a Josephson traveling-wave parametric am- plifier (JTWPA) as a quantum source of broadband microwave entangled photons for detecting very low cross-radar section objects is described. Microwave entangled signal-idler pairs at 3.3 GHz and 3.45 GHz are generated, respectively, with a wide bandwidth equal to 3 GHz, a power gain equal to 15.3 dB, and a noise temperature close to the standard quantum limit (SQL) at cryogenic temperatures. A phase conjugate receiver is used as a joint detection scheme for entangled signal-idler pairs, and the expected performance of the scheme in terms of the corresponding receiver operating characteristic (ROC) curve is obtained. These results in terms of maximum dynamic bandwidth and ROC candidate our proposed scheme towards a long-range target detection MQR. </p
... Photonics quantum sensing technology is largely proposed for its simplicity compared to electronics quantum sensing [5], [6]. Recently, the generation of quantum signals at microwaves has been proved [7], [8], [9], [10], [11], [12], [13], [14], paving the way to microwave quantum radars (MQRs). In 2019, Luong et al. presented the first microwave quantum radar operating with microwave entangled photons [4]. ...
... where we have introduced the parameter d P CR = √ MN 1 /σ 1 = 2 M κN S (N S + 1)/(N B + 1)(2N S + 1), and the new threshold parametrization as ln η = (s − 1/2)d 2 P CR . The corresponding ROC curves obtained from Eqs. (10)- (11) and Eqs. (12)- (13) and shown in Fig. 12 are practically indistinguishable in the considered regime. ...
... The full blue curve refers to QI with PCR detection: Eqs. (10)-(11) and Eqs. (12)-(13) provide indistinguishable curves for the chosen parameters, N S = 0.05, N B = 100, κ = 0.01, M = 1.5 × 10 7 . ...
p>In this article, the current status of a novel mi- crowave quantum radar (MQR) based on quantum illumination (QI) protocol using a Josephson traveling-wave parametric am- plifier (JTWPA) as a quantum source of broadband microwave entangled photons for detecting very low cross-radar section objects is described. Microwave entangled signal-idler pairs at 3.3 GHz and 3.45 GHz are generated, respectively, with a wide bandwidth equal to 3 GHz, a power gain equal to 15.3 dB, and a noise temperature close to the standard quantum limit (SQL) at cryogenic temperatures. A phase conjugate receiver is used as a joint detection scheme for entangled signal-idler pairs, and the expected performance of the scheme in terms of the corresponding receiver operating characteristic (ROC) curve is obtained. These results in terms of maximum dynamic bandwidth and ROC candidate our proposed scheme towards a long-range target detection MQR. </p
... Two-mode squeezing in superconducting circuits has been demonstrated in narrow-band Josephson parametric amplifiers based on resonant structures [19][20][21][22][23][24][25][26], semi infinite transmission lines via Dynamical Casimir Effect [27][28][29] and surface acoustic wave hybrid systems [30]. ...
Traveling wave parametric amplifiers (TWPAs) have recently emerged as essential tools for broadband near quantum-limited amplification. However, their use to generate microwave quantum states still misses an experimental demonstration. In this Letter, we report operation of a TWPA as a source of two-mode squeezed microwave radiation. We demonstrate broadband entanglement generation between two modes separated by up to 400 MHz by measuring logarithmic negativity between 0.27 and 0.51 and collective quadrature squeezing below the vacuum limit between 1.5 and 2.1 dB. This work opens interesting perspectives for the exploration of novel microwave photonics experiments with possible applications in quantum sensing and continuous variable quantum computing.
... I conclude by noting that the technical challenges associated with implementing a quantum squeezed receiver within an axion search have been overcome. In particular, Josephson parametric amplifiers (JPAs) are now a routine piece of quantum technology [9,44,48,49], which prepare one and two-mode squeezed states of microwave resonators and measure (by amplification) single microwave quadratures. Recently two JPAs have been combined to realize the configuration in Fig. 4, creating a factor of two increase in axion scan rate over the CSL value [5]. ...
These notes summarize lectures given at the 2019 Les Houches summer school on
Quantum Information Machines. They describe and review an application of
quantum metrology concepts to searches for ultralight dark matter. In
particular, for ultralight dark matter that couples as a weak classical force
to a laboratory harmonic oscillator, quantum squeezing benefits experiments in
which the mass of the dark matter particle is unknown. This benefit is present
even if the oscillatory dark matter signal is much more coherent than the
harmonic oscillator that it couples to, as is the case for microwave frequency
searches for dark matter axion particles.
... Two-mode squeezing in superconducting circuits has been demonstrated in narrow-band Josephson parametric amplifiers based on resonant structures [19][20][21][22][23][24][25][26], semi infinite transmission lines via Dynamical Casimir Effect [27][28][29] and surface acoustic wave hybrid systems [30]. ...
Traveling wave parametric amplifiers (TWPAs) have recently emerged as essential tools for broadband near quantum-limited amplification. However, their use to generate microwave quantum states still misses an experimental demonstration. In this letter, we report operation of a TWPA as a source of two-mode squeezed microwave radiation. We demonstrate broadband entanglement generation between two modes separated by up to 400 MHz by measuring logarithmic negativity between 0.27 and 0.51 and collective quadrature squeezing below the vacuum limit between 1.5 and 2.1 dB. This work opens interesting perspectives for the exploration of novel microwave photonics experiments with possible applications in quantum sensing and continuous variable quantum computing.
... I conclude by noting that the technical challenges associated with implementing a quantum squeezed receiver within an axion search have been overcome. In particular, Josephson parametric amplifiers (JPAs) are now a routine piece of quantum technology [9,[45][46][47], which prepare one and two-mode squeezed states of microwave resonators and measure (by amplification) single microwave quadratures. Recently two JPAs have been combined to realize the configuration in Fig. 4, creating a factor of two increase in axion scan rate over the CSL value [5]. ...
These notes summarize lectures given at the 2019 Les Houches summer school on Quantum Information Machines. They describe and review an application of quantum metrology concepts to searches for ultralight dark matter. In particular, for ultralight dark matter that couples as a weak classical force to a laboratory harmonic oscillator, quantum squeezing benefits experiments in which the mass of the dark matter particle is unknown. This benefit is present even if the oscillatory dark matter signal is much more coherent than the harmonic oscillator that it couples to, as is the case for microwave frequency searches for dark matter axion particles.
... The system gain G i and system noise n add, i of both signal and idler measurement chains are calibrated by injecting a known amount of thermal noise using two temperature-controlled 50-ohm cold loads (26,42). The calibrators are attached to the measurement setup with two copper coaxial cables of the same length and material as the cables used to connect the JPC via two latching microwave switches (Radiall R573423600). ...
Quantum illumination uses entangled signal-idler photon pairs to boost the detection efficiency of low-reflectivity objects in environments with bright thermal noise. Its advantage is particularly evident at low signal powers, a promising feature for applications such as noninvasive biomedical scanning or low-power short-range radar. Here, we experimentally investigate the concept of quantum illumination at microwave frequencies. We generate entangled fields to illuminate a room-temperature object at a distance of 1 m in a free-space detection setup. We implement a digital phase-conjugate receiver based on linear quadrature measurements that outperforms a symmetric classical noise radar in the same conditions, despite the entanglement-breaking signal path. Starting from experimental data, we also simulate the case of perfect idler photon number detection, which results in a quantum advantage compared with the relative classical benchmark. Our results highlight the opportunities and challenges in the way toward a first room-temperature application of microwave quantum circuits.
... This is because the equation neglects anything related to non-linearities, losses and noise. Similarly to Ref. [32], we include measurement noises and losses in the presented results. Photon losses in the system and the nonlinearity [24] in the SQUID result in lower cross-correlation values. ...
Entangled pairs of microwave photons are commonly produced in the narrow frequency band of a resonator, which represents a modified vacuum density of states. We generate and investigate the entanglement of a stream of photon pairs, generated in a semi-infinite broadband transmission line, terminated by a superconducting quantum interference device (SQUID). A weak pump signal modulates the SQUID inductance, resulting in a single time-varying boundary condition, and we detect all four quadratures of the microwave radiation emitted at two different frequencies separated by 0.7 GHz. Power calibration is done in situ, and we find positive logarithmic negativity and two-mode squeezing below the vacuum in the observed radiation, indicating entanglement.
... 2019年, Li等 [ [73] ; (b) 20 dB功分器结构图 [73] ; ...
... 2019年, Li等 [ [73] ; (b) 20 dB功分器结构图 [73] ; ...
... 19. (a) Structure of quadrature hybrid coupler [73] ; ...
As a novel hybrid quantum system, cavity optomechanical system shows super strong coupling strength, extremely low noise level and considerable coherent time under superconducting condition. In this paper, we briefly introduce basic principles of cavity optomechanics and cavity optomechanical systems. Meanwhile, we also classify the widely studied cavity optomechanical systems as five categories in their materials and structures. Significant parameters of these optomechanical systems, such as quality factor, mass and vibrating frequency of mechanical oscillator, are listed in detail. Technical merits and defects of these optomechanical systems are summarized. Furthermore, we introduce the research progress of non-classical microwave quantum states preparation by utilizing generalized cavity optomechanical systems, and we also analyze the performance advancements and remaining problems of this preparation method. In the end, we summarize the application cases at present and look forward to the potential application scenarios in the future. Our summary may be helpful for researchers who are focusing on quantum applications in sensing, radar, navigation, and communication in microwave domain.
... Quantum sensing is well developed for photonic applications [1] inline with other advanced areas of quantum information [2][3][4][5]. As a matter of fact, quantum optics has been so far the most natural and convenient setting for implementing the majority of protocols in quantum communication, cryptography and metrology [6]. ...
... This is accomplished by probing the target with a few entangled photons per mode, in a stealthy non-invasive fashion which is impossible to reproduce with classical means. In the Gaussian version of the protocol [12], the light is prepared in a two mode squeezed vacuum state [3] with the signal mode sent to probe the target while the idler mode is kept at the receiver. Even though entanglement is lost in the round trip from the target, the surviving signal-idler correlations are strong enough to beat the performance achievable by any coherent-state transmitter using the same number of photons and bandwidth. ...
... The system gain G i and system noise n add,i of both signal and idler measurement chains are calibrated by injecting a known amount of thermal noise using two temperature controlled 50 Ω cold loads [2,3]. The calibrators are attached to the measurement setup with two copper coaxial cables of the same length and material as the cables used to connect the JPC via two latching microwave switches (Radiall R573423600). ...
Quantum illumination is a powerful sensing technique which employs entangled photons to boost the detection of low-reflectivity objects in environments with bright thermal noise. The promised advantage over classical strategies is particularly evident at low signal photon flux, a feature which makes the protocol an ideal prototype for non-invasive biomedical scanning or low-power short-range radar detection. In this work we experimentally demonstrate quantum illumination at microwave frequencies. We generate entangled fields using a Josephson parametric converter at millikelvin temperatures to illuminate a room-temperature object at a distance of 1 meter in a proof of principle bistatic radar setup. Using heterodyne detection and suitable data-processing at the receiver we observe an up to three times improved signal-to-noise ratio compared to the classical benchmark, the coherent-state transmitter, outperforming any classically-correlated radar source at the same signal power and bandwidth. Quantum illumination is a first room-temperature application of microwave quantum circuits demonstrating quantum supremacy in detection and sensing.
