Abstract Quantum transducers between microwave and optical photons are essential for long-distance quantum networks based on superconducting qubits. An optically active self-assembled quantum dot molecule (QDM) is an attractive platform for the implementation of a quantum transducer because an exciton in a QDM can be efficiently coupled to both optical and microwave fields at the single-photon level. Recently, the transduction between microwave and optical photons has been demonstrated with a QDM integrated with a superconducting resonator. In this paper, we present a design of a QD-high impedance resonator device with a low microwave loss and an expected large single-microwave photon coupling strength of 100s of MHz. We integrate self-assembled QDs onto a high-impedance superconducting resonator using a transfer printing technique and demonstrate a low-microwave loss rate of 1.8 MHz and gate tunability of the QDs. The corresponding microwave photon decay time of 88 ns is longer than the time necessary for the optical-microwave transduction process as well as the transmon-resonator swap operation time. This feature will facilitate efficient quantum transduction between an optical and microwave qubit.
Abstract Quantum transducers between microwave and optical photons are essential for long-distance quantum networks based on superconducting qubits. An optically active self-assembled quantum dot molecule (QDM) is an attractive platform for the implementation of a quantum transducer because an exciton in a QDM can be efficiently coupled to both optical and microwave fields at the single-photon level. Recently, the transduction between microwave and optical photons has been demonstrated with a QDM integrated with a superconducting resonator. In this paper, we present a design of a QD-high impedance resonator device with a low microwave loss and an expected large single-microwave photon coupling strength of 100s of MHz. We integrate self-assembled QDs onto a high-impedance superconducting resonator using a transfer printing technique and demonstrate a low-microwave loss rate of 1.8 MHz and gate tunability of the QDs. The corresponding microwave photon decay time of 88 ns is longer than the time necessary for the optical-microwave transduction process as well as the transmon-resonator swap operation time. This feature will facilitate efficient quantum transduction between an optical and microwave qubit.
Quantum transduction between the microwave and optical domains is an outstanding challenge for long-distance quantum networks based on superconducting qubits.For all transducers realized to date, the generally weak light-matter coupling does not allow high transduction efficiency, large bandwidth, and low noise simultaneously.Here we show that a large electric dipole moment of an exciton in an optically active self-assembled quantum dot molecule (QDM) efficiently couples to a microwave resonator field at the single-photon level.This allows for transduction between microwave and optical photons without coherent optical pump fields to enhance the interaction.With an on-chip device, we demonstrate a sizeable single-photon coupling strength of 16 MHz.Thanks to the fast exciton decay in the QDM, the transduction bandwidth between an optical and microwave resonator photon reaches several 100 s of MHz.We also show that the transduction process via the QDM is fully coherent within the measurement error range.
The successes of superconducting quantum circuits at local manipulation of quantum information and photonics technology at long-distance transmission of the same have spurred interest in the development of quantum transducers for efficient, low-noise, and bidirectional frequency conversion of photons between the microwave and optical domains. We propose to realize such functionality through the coupling of electrical, piezoelectric, and optomechanical resonators. The coupling of the mechanical subsystems enables formation of a resonant mechanical supermode that provides a mechanically-mediated, efficient single interface to both the microwave and optical domains. The conversion process is analyzed by applying an equivalent circuit model that relates device-level parameters to overall figures of merit for conversion efficiency η and added noise N. These can be further enhanced by proper impedance matching of the transducer to an input microwave transmission line. The performance of potential transducers is assessed through finite-element simulations, with a focus on geometries in GaAs, followed by considerations of the AlN, LiNbO3, and AlN-on-Si platforms. We present strategies for maximizing η and minimizing N, and find that simultaneously achieving η>50% and N<0.5 should be possible with current technology. Our comprehensive analysis of the full transduction chain enables us to outline a development path for the realization of high-performance quantum transducers that will constitute a new resource for quantum information science.
The successes of superconducting quantum circuits at local manipulation of quantum information and photonics technology at long-distance transmission of the same have spurred interest in the development of quantum transducers for efficient, low-noise, and bidirectional frequency conversion of photons between the microwave and optical domains. We propose to realize such functionality through the coupling of electrical, piezoelectric, and optomechanical resonators. The coupling of the mechanical subsystems enables formation of a resonant mechanical supermode that provides a mechanically mediated, efficient single interface to both the microwave and optical domains. The conversion process is analyzed by applying an equivalent circuit model that relates device-level parameters to overall figures of merit for conversion efficiency $\ensuremath{\eta}$ and added noise N. These can be further enhanced by proper impedance matching of the transducer to an input microwave transmission line. The performance of potential transducers is assessed through finite-element simulations, with a focus on geometries in GaAs, followed by considerations of the AlN, LiNbO3, and AlN-on-Si platforms. We present strategies for maximizing $\ensuremath{\eta}$ and minimizing N, and find that simultaneously achieving $\ensuremath{\eta}>50\mathrm{%}$ and N<0.5 should be possible with current technology. We find that the use of a mechanical supermode for mediating transduction is a key enabler for high-efficiency operation, particularly when paired with an appropriate microwave impedance-matching network. Our comprehensive analysis of the full transduction chain enables us to outline a development path for the realization of high-performance quantum transducers that will constitute a valuable resource for quantum information science.
Abstract Optical quantum networks can connect distant quantum processors to enable secure quantum communication and distributed quantum computing. Superconducting qubits are a leading technology for quantum information processing but cannot couple to long-distance optical networks without an efficient, coherent, and low noise interface between microwave and optical photons. Here, we demonstrate a microwave-to-optical transducer using an ensemble of erbium ions that is simultaneously coupled to a superconducting microwave resonator and a nanophotonic optical resonator. The coherent atomic transitions of the ions mediate the frequency conversion from microwave photons to optical photons and using photon counting we observed device conversion efficiency approaching 10 −7 . With pulsed operation at a low duty cycle, the device maintained a spin temperature below 100 mK and microwave resonator heating of less than 0.15 quanta.
Quantum networks of superconducting circuit quantum processors are an exciting prospect but are unfeasible without an efficient quantum interface between optical light and superconducting qubits. This problem motivates the development of a quantum microwave-to-optical transducer, a device that can faithfully transfer the state of a superconducting circuit to a photonic flying qubit and vice versa. This thesis describes our progress towards building a microwave-to-optical transducer mediated by phonons in a high-overtone bulk acoustic resonator (HBAR). Novel aluminum nitride-on-quartz HBARs are designed, fabricated, and tested. The acoustic loss rates are found to be near the state-of-the-art. Transduction-compatible transmon qubits are designed and tested. These qubits are capable of operating inside an optical cavity as well as achieving electromechanical interactions in the strong-coupling regime. An initial experiment studied how superconducting qubits recover after exposure to infrared light and demonstrated that the transduction-compatible qubits should be able to operate in a transducer with a reasonable duty cycle. The concept of microwave-to-optical transduction using multiple acoustic modes is established, and new simulation methods are developed to rapidly optimize HBARs. These tools are used to create a transduction-compatible qubit-HBAR device operating in the multi-mode strong coupling regime. Separately, a transduction compatible optical cavity was built and used to perform optomechanical measurements of a transduction-compatible HBAR and confirm that this device can reach the high-cooperativity regime. Finally, a measurement for verifying that a transducer is operating as a source of single photons is discussed. This can be accomplished by measuring the optical second-order correlation function of transduced photons. A filter cavity cascade is constructed to perform this measurement without being overwhelmed by optical pump leakage. These results establish bulk acoustic transduction as a promising platform for low-noise quantum microwave-to-optical transduction.
Microwave-to-optical transducers facilitate the distributed quantum network by combining the high-speed information-processing abilities of superconducting circuits with the long-distance, low-loss transmitting capabilities of optical photons. Besides core metrics such as high efficiency, low noise, and wide bandwidth, practical and scalable transducers also demand a compact footprint and frequency tunability. In this work, we propose an integrated and tunable transducer that combines a coplanar waveguide microwave resonator with a magno-optomechanical microcavity via flip-chip bonding. Benefiting from the broad frequency tunability of the magnon mode, the working frequency range can be tuned over several gigahertz. Through optimization of the geometry and pump powers, our design achieves a theoretical microwave-to-optical photon conversion efficiency exceeding 50% using experimentally achievable parameters, alongside a bandwidth greater than 10 kHz. An added noise near the quantum limit $(\ensuremath{\sim}1)$ is achievable at 10 mK using lower pump powers at the cost of conversion efficiency or a pulsed-pump protocol. By merging compact integration with wide frequency tunability, this platform offers a promising pathway toward scalable quantum networks.