Single-shot read-out of a superconducting qubit using a Josephson parametric oscillator

Abstract

We propose and demonstrate a read-out technique for a superconducting qubit by dispersively coupling it with a Josephson parametric oscillator. We employ a tunable quarter wavelength superconducting resonator and modulate its resonant frequency at twice its value with an amplitude surpassing the threshold for parametric instability. We map the qubit states onto two distinct states of classical parametric oscillation: one oscillating state, with 185±15 photons in the resonator, and one with zero oscillation amplitude. This high contrast obviates a following quantum-limited amplifier. We demonstrate proof-of-principle, single-shot read-out performance, and present an error budget indicating that this method can surpass the fidelity threshold required for quantum computing.

Nondegenerate parametric oscillations in a tunable superconducting resonator

“…The JPO can be used for vacuum squeezing and photonic entanglement [13,14], photonic qubit operation [15], and catstate engineering [16][17][18]. The JPO has also been employed for high-fidelity readout of superconducting qubits [19,20].…”

Nondegenerate Parametric Resonance in a Tunable Superconducting Cavity

“…A novel generation of quantum limited parametric amplifiers 1-9 makes possible single shot readout and continuous monitoring of states of superconducting qubits [10][11][12][13][14] . Noise squeezing under parametric down-conversion 15 is used to enhance the qubit coherence time 16,17 .…”

Period-tripling subharmonic oscillations in a driven superconducting resonator

“…More recent reports concern subharmonic resonances in lasers 19,20 . In Josephson circuits, the period-multiplying phenomenon has not received much attention; instead, research was focused on transition to chaos 21,22 and lately on bifurcation phenomena 23,24 and parametric oscillations 5,6,[25][26][27] . Only recently, subharmonic oscillations in the quantum regime were theoretically discussed in the context of cQED 16,28,29 .…”