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arXiv:2507.22641 · Advanced Quantum Technologies

Single‐ and Two‐Mode Squeezing by Modulated Coupling to a Rabi Driven Qubit

Eliya Blumenthal, Nir Gutman, Ido E. Kaminer, Shay Hacohen-Gourgy

Published Mar 1, 2026• 0 citations
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Abstract

ABSTRACT Advanced bosonic quantum computing architectures demand nonlocal Gaussian operations such as two‐mode squeezing to unlock universal control, enable entanglement generation, and implement logical operations across distributed modes. This work presents a novel method for generating conditional squeezing using a Rabi‐driven qubit dispersively coupled to one or two harmonic oscillators. A proof that this enables universal control over bosonic modes is provided, expanding the toolkit for continuous‐variable quantum information processing. Using modulated Jaynes–Cummings interactions in circuit QED, the simulation predicts intra‐cavity squeezing of 13dB (single‐mode), 4dB (superimposed single‐mode), and 12dB (two‐mode), with the latter two yet to be demonstrated experimentally. These results establish a new paradigm for qubit‐conditioned control of photonic states, with applications to quantum sensing and continuous‐variable computation on readily available systems.

DOI
10.1002/qute.202500490

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ABSTRACT Advanced bosonic quantum computing architectures demand nonlocal Gaussian operations such as two‐mode squeezing to unlock universal control, enable entanglement generation, and implement logical operations across distributed modes. This work presents a novel method for generating conditional squeezing using a Rabi‐driven qubit dispersively coupled to one or two harmonic oscillators. A proof that this enables universal control over bosonic modes is provided, expanding the toolkit for continuous‐variable quantum information processing. Using modulated Jaynes–Cummings interactions in circuit QED, the simulation predicts intra‐cavity squeezing of 13dB (single‐mode), 4dB (superimposed single‐mode), and 12dB (two‐mode), with the latter two yet to be demonstrated experimentally. These results establish a new paradigm for qubit‐conditioned control of photonic states, with applications to quantum sensing and continuous‐variable computation on readily available systems.
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Bosonic encoding is an approach for quantum information processing, promising lower hardware overhead by encoding in the many levels of a harmonic-oscillator mode. Scaling to multiple modes requires weak interaction for independent control, yet strong interaction for fast control. Applying fast and efficient universal control on multiple modes remains an open problem. Surprisingly, we find that displacements conditioned on the state of a single-qubit ancilla coupled to multiple harmonic oscillators are sufficient for universal control. We present the conditional- operation concept, which can be used to reduce the duration of entangling gates. Within this guiding concept, we develop the conditional- displacement control method which enables fast generation and control of bosonic states in multimode systems weakly coupled to a single-ancilla qubit. Our method is fast despite the weak ancilla coupling. The weak coupling in turn allows for excellent separability and thus independent control. We demonstrate our control on a superconducting transmon qubit weakly coupled to a multimode superconducting cavity. We create both entangled and separable cat states in different modes of the multimode cavity, showing entangling operations at low crosstalk while maintaining independent control of the different modes. We show that the operation time is not limited by the inverse of the coupling rate, which is the typical timescale, and we exceed it by almost 2 orders of magnitude. We verify our results with an efficient method for measurement of the multimode characteristic function which employs our conditional- displacement. Our results inspire a new approach toward general entangling operations and allow for fast and efficient multimode bosonic encoding and measurement. Published by the American Physical Society 2024
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