Efficient one- and two-qubit pulsed gates for an oscillator stabilized Josephson qubit

TL;DR

This paper proposes theoretical high-fidelity pulsed gate schemes for superconducting flux qubits, optimizing for noise resilience and tunability, with detailed analysis of fidelity limitations and pulse shaping.

Contribution

It introduces tailored pulse schemes for high-fidelity single- and two-qubit gates in an IBM flux qubit, addressing noise and control errors.

Findings

Gates achieve 1% fidelity loss due to 1/f noise with 20-30ns pulses for single-qubit gates.

Two-qubit controlled-Z gate achieved in about 60ns with comparable fidelity loss.

Control phase imprecision is identified as the main fidelity limitation.

Abstract

We present theoretical schemes for performing high-fidelity one- and two-qubit pulsed gates for a superconducting flux qubit. The "IBM qubit" consists of three Josephson junctions, three loops, and a superconducting transmission line. Assuming a fixed inductive qubit-qubit coupling, we show that the effective qubit-qubit interaction is tunable by changing the applied fluxes, and can be made negligible, allowing one to perform high fidelity single qubit gates. Our schemes are tailored to alleviate errors due to 1/f noise; we find gates with only 1% loss of fidelity due to this source, for pulse times in the range of 20-30ns for one-qubit gates (Z rotations, Hadamard), and 60ns for a two-qubit gate (controlled-Z). Our relaxation and dephasing time estimates indicate a comparable loss of fidelity from this source. The control of leakage plays an important role in the design of our shaped pulses, preventing shorter pulse times. However, we have found that imprecision in the control of the quantum phase plays the major role in the limitation of the fidelity of our gates.