Broadband Continuous-Variable Entanglement Generation Using a Kerr-Free Josephson Metamaterial

Abstract

Entangled microwave photons form a fundamental resource for quantum information processing and sensing with continuous variables. We use a low-loss Josephson metamaterial comprising superconducting, nonlinear, asymmetric inductive elements to generate frequency-entangled photons from vacuum fluctuations at a rate of 2 giga entangled bits per second spanning over the 4-GHz bandwidth. The device is operated as a traveling-wave parametric amplifier under Kerr-relieving biasing conditions. Furthermore, we demonstrate single-mode squeezing in such devices-3.1 ± 0.7 dB below the zero-point level at half of modulation frequency.

Generation and Structuring of Multipartite Entanglement in a Josephson Parametric System

“…The basic parametric microwave setting allows for enhancement in the number of spectral modes by additional pump tones, which leads to generation of more complex, entangled $$\mathcal {\tilde{H}}$$‐graph states. Enhanced number of modes requires larger bandwidth, which calls for broadband parametric devices such as TWPAs [ 60–64 ] or broadband JPAs [ 59,65 ] in order to avoid problems with spectral mode crowding.…”

“…Furthermore, by tuning the phases of the pumps, the state can be converted into square-lattice H-graph state. With the bandwidth improvements provided by the state-of-the-art superconducting parametric devices, such as the broadband, low-loss travelling wave parametric amplifier, [62][63][64] we expect a substantial increase in the number of entangled modes, which facilitates generation of highly-squeezed square-lattice H-graph states for CV quantum computation at microwave frequencies.…”

Microwave Quantum Radar based on a Josephson Traveling wave Parametric Amplifier and a Phase-Conjugate Receiver

“…The distribution of non-linearity over the entire device and the elimination of resonant structures allow the generation of fields with substantial squeezing in a high dynamic range and an emission of broadband microwave entangled states [22], [23].…”

Vulnerability to Parameter Spread in Josephson Traveling-Wave Parametric Amplifiers

“…JTWPAs utilize the nonlinear inductance of Josephson junctions, arranged as transmission line arrays of either single Josephson junctions [4]- [7], dc superconducting quantum interference devices (SQUIDs) [8], rf-SQUIDs [9], or superconducting nonlinear asymmetric inductive elements (SNAILs) [10]- [13]. Parametric amplification occurs, depending on the order of nonlinearity, in the three-wave-mixing (3WM) or four-wave-mixing (4WM) regime, with f p = f s + f i and Manuscript received November 18, 2022; accepted January 18, 2023.…”