Universal composite phase gates with tunable target phase

TL;DR

This paper introduces a systematic method for designing universal composite phase gates with tunable target phases, offering high robustness against control errors and broad applicability in quantum information processing.

Contribution

It develops a general analytic framework for constructing robust, tunable phase gates using composite pulses based on Cayley--Klein parametrization, valid for arbitrary pulse shapes.

Findings

Numerical simulations show high-order error suppression.

Gates exhibit broad high-fidelity plateaus over wide error ranges.

Method provides intrinsic robustness against control imperfections.

Abstract

We present a systematic method for constructing universal composite phase gates with a continuously tunable target phase. Using a general Cayley--Klein parametrization of the single-pulse propagator, we design gates from an even number of nominal $\pi$ pulses and derive analytic phase families by canceling, order by order in a small deviation parameter, the leading contributions to the undesired off-diagonal element of the composite propagator, independently of the dynamical phase. The resulting sequences provide intrinsic robustness against generic control imperfections and parameter fluctuations and remain valid for arbitrary pulse shapes. Numerical simulations in a standard two-level model confirm high-order error suppression and demonstrate broad, flat high-fidelity plateaus over wide ranges of simultaneous pulse-area and detuning errors, highlighting the efficiency of the proposed universal composite phase gates for resilient phase control in quantum information processing.