Iterative quantum phase estimation with cQED encoding

• URL: http://arxiv.org/abs/2606.22071v1
• Date: Sat, 20 Jun 2026 14:45:05 GMT
• Title: Iterative quantum phase estimation with cQED encoding
• Abstract summary: Quantum phase estimation is a cornerstone algorithm for determining eigenvalues of unitary operators or Hamiltonians.<n>We propose a conceptually simple and experimentally feasible alternative that exploits the toolbox of circuit quantum electrodynamics.<n>A bosonic mode serves as an efficient quantum memory in which the binary digits of the phase are encoded into the direction of phase-space rotations.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Quantum phase estimation is a cornerstone algorithm for determining eigenvalues of unitary operators or Hamiltonians with Heisenberg-limited precision. Conventional implementations rely on deep controlled-unitary operations together with an inverse quantum Fourier transform, resulting in substantial circuit depth and hardware overhead. Here, we propose a conceptually simple and experimentally feasible alternative that exploits the toolbox of circuit quantum electrodynamics. The protocol extracts the phase through a sequence of binary threshold tests, eliminating the need for an inverse quantum Fourier transform. A bosonic mode serves as an efficient quantum memory in which the binary digits of the phase are encoded into the direction of phase-space rotations. These digits are then read out sequentially via high-fidelity homodyne measurements. We show that the protocol achieves Heisenberg scaling in estimation precision while simultaneously providing exponentially suppressed failure probability. By replacing the ancillary circuit with a bosonic degree of freedom, the scheme significantly reduces hardware complexity and offers a practical route toward implementing high-precision quantum phase estimation on circuit quantum electrodynamics platforms.

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