Quantum Gate for Kerr Nonlinear Parametric Oscillator Using Effective Excited States

Abstract

A Kerr-nonlinear parametric oscillator (KPO) can stabilize a quantum superposition of two coherent states with opposite phases, which can be used as a qubit. In a universal gate set for quantum computation with KPOs, an Rx gate, which interchanges the two coherent states, is relatively hard to perform owing to the stability of the two states. We propose a method for a high-fidelity Rx gate by exciting the KPO outside the qubit space parity-selectively, which can be implemented by only adding a driving field. In this method, utilizing higher effective excited states leads to a faster Rx gate, rather than states near the qubit space. The proposed method can realize a continuous Rx gate, and thus is expected to be useful for, e.g., recently proposed variational quantum algorithms.

Effective spin models of Kerr-nonlinear parametric oscillators for quantum annealing

“…The physical implementation of QA with KPOs is also expected [18,20,24,27]. Qubits generated by the adiabatic process for KPOs can be utilized for the gate-based quantum computation [17,31,[33][34][35][36][37][38].…”

Autonomous Quantum Error Correction in a Four-Photon Kerr Parametric Oscillator

“…Since this fourphoton pump cannot be achieved by simple linear driving and must be achieved by parametric modulation of the Josephson junction energy [27,28] (see Supplementary Note 1), we term this system a four-photon Kerr parametric oscillator (KPO). Although a KPO has received much attention very recently because of its use for the generation and stabilization of the cat states [29-36, 38, 72], gate-based quantum computation [30,34,[38][39][40][41][42], measurement-based error correction [43,44], quantum annealing [45][46][47][48][49][50][51], and other physically interesting topics [52][53][54][55][56][57][58][59], little attention has been paid to its applicability to AQEC. Our study reveals that a KPO can be a suitable system for AQEC.…”

Chaos in coupled Kerr-nonlinear parametric oscillators

“…Quantum annealing using KPOs has been developed in this five years [30][31][32][33][34][35]. The KPOs can also be used for qubits in gate-based quantum computing [21,[36][37][38][39][40]. Since the KPO qubit, also known as a Kerr-cat qubit, is robust against bit-flip errors, like the above dissipativetype qubit, fault-tolerant quantum computation using KPOs has been developed [41,42].…”