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arXiv:2406.05007 · Physical Review Research

Slow and stored light via electromagnetically induced transparency using a Λ -type superconducting artificial atom

Kai-I Chu, Xiao-Cheng Lu, Kuan-Hsun Chiang, Yen‐Hsiang Lin, Chii‐Dong Chen, Ite A. Yu, Wen-Te Liao, Yung‐Fu Chen

Published Jan 21, 2025• 13 citations
arXivHTMLPDF

Abstract

Recent progresses in Josephson-junction-based superconducting circuits have propelled quantum information processing forward. However, the lack of a metastable state in most superconducting artificial atoms hinders the development of photonic quantum memory in this platform. Here we use a single superconducting qubit-resonator system to realize a desired Λ -type artificial atom, and to demonstrate slow light with a group velocity of 3.6 km/s and the microwave storage with a memory time extending to several hundred nanoseconds via electromagnetically induced transparency. Our results highlight the potential of achieving microwave quantum memory, promising substantial advancements in quantum information processing within superconducting circuits.

DOI
10.1103/physrevresearch.7.l012015

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Recent progresses in Josephson-junction-based superconducting circuits have propelled quantum information processing forward. However, the lack of a metastable state in most superconducting artificial atoms hinders the development of photonic quantum memory in this platform. Here we use a single superconducting qubit-resonator system to realize a desired Λ -type artificial atom, and to demonstrate slow light with a group velocity of 3.6 km/s and the microwave storage with a memory time extending to several hundred nanoseconds via electromagnetically induced transparency. Our results highlight the potential of achieving microwave quantum memory, promising substantial advancements in quantum information processing within superconducting circuits.
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We investigate theoretically a type of microwave memory that is composed of a single transmon qubit and a coupling resonator. The synergy of the parametric modulation of the qubit resonance frequency and a microwave directly driving the qubit transition can constitute effective three-level $\mathrm{\ensuremath{\Lambda}}$-type electromagnetically induced transparency. We demonstrate that the dynamical control of such a parametric modulation allows for the possibility of microwave storage and retrieval using a single qubit. Our results pave the way towards the practical implementation of quantum information in superconducting circuits.
The rapid progress in quantum information processing leads to a rising demand for devices to control the propagation of electromagnetic wave pulses and to ultimately realize universal and efficient quantum memory. While in recent years, significant progress has been made to realize slow light and quantum memories with atoms at optical frequencies, superconducting circuits in the microwave domain still lack such devices. Here, we demonstrate slowing down electromagnetic waves in a superconducting metamaterial composed of eight qubits coupled to a common waveguide, forming a waveguide quantum electrodynamics system. We analyze two complementary approaches, one relying on dressed states of the Autler–Townes splitting and the other based on a tailored dispersion profile using the qubits tunability. Our time-resolved experiments show reduced group velocities of down to a factor of about 1500 smaller than in vacuum. Depending on the method used, the speed of light can be controlled with an additional microwave tone or an effective qubit detuning. Our findings demonstrate high flexibility of superconducting circuits to realize custom band structures and open the door to microwave dispersion engineering in the quantum regime.
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Significant advances in coherence render superconducting quantum circuits a viable platform for fault-tolerant quantum computing. To further extend capabilities, highly coherent quantum systems could act as quantum memories for these circuits. A useful quantum memory must be rapidly addressable by Josephson-junction-based artificial atoms, while maintaining superior coherence. We demonstrate a superconducting microwave cavity architecture that is highly robust against major sources of loss that are encountered in the engineering of circuit QED systems. The architecture allows for storage of quantum superpositions in a resonator on the millisecond scale, while strong coupling between the resonator and a transmon qubit enables control, encoding, and readout at MHz rates. This extends the maximum available coherence time attainable in superconducting circuits by almost an order of magnitude compared to earlier hardware. Our design is an ideal platform for studying coherent quantum optics and marks an important step towards hardware-efficient quantum computing in Josephson-junction-based quantum circuits.