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arXiv:2601.13923

Universal composite phase gates with tunable target phase

Peter Chernev, Mouhamad Al-Mahmoud, Andon A. Rangelov

quant-phphysics.atom-phSubmitted Jan 20, 2026• Announced Jan 21, 2026• 0 citations
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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 $π$ 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.

Comments
8 pages, 5 figures

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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 πππ 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.
We present a method to construct high-fidelity quantum phase gates, which are insensitive to errors in various experimental parameters. The phase gates consist of a pair of two sequential broadband composite pulses, with a phase difference $\ensuremath{\pi}+\ensuremath{\alpha}/2$ between them, where $\ensuremath{\alpha}$ is the desired gate phase. By using composite pulses which compensate systematic errors in the pulse area, the frequency detuning, or both the area and the detuning, we thereby construct composite phase gates which compensate errors in the same parameters. Particularly interesting are phase gates which use the recently discovered universal composite pulses, which compensate systematic errors in any parameter of the driving field, which keep the evolution Hermitian (e.g., pulse amplitude and duration, pulse shape, frequency detuning, Stark shifts, residual frequency chirps, etc.).
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Abstract We construct composite half- π pulses that are simultaneously robust to systematic mistracking of the control phases and to small pulse-area deviations. We extend the errant-phase composite-pulse approach from population-inversion ( π ) gates to π / 2 rotations, which are intrinsically more sensitive to phase miscalibration because they rely on controlled interference to create a specific superposition. The phases of the constituent pulses are chosen to cancel, order by order, the leading error terms associated with a correlated phase-scaling parameter while preserving broadband tolerance to pulse-area errors. We provide explicit non-anagram phase solutions for odd-length sequences and verify their performance by numerical simulations of the full composite propagator.
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