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Quantum Transducer Characterization and Protocols
Summary
A collaborative team working to develop optical interconnects between superconducting quantum computers for the first time.
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Optical Networking of Superconducting Quantum Computers with Transducer Devices
Description
Transducer devices which exchange quantum states between GHz-microwave and THz-optical frequencies are a critical element necessary to optically network superconducting quantum computers to allow their computational power to scale beyond the confines of a single cryostat. To preserve quantum states in a network, transducers of various types must operate with high efficiency (> 50%) while adding very little noise (< 1 photon). Sophisticated metrology is required to quantify the quantum performance of these novel devices, characterize operating parameters to guide design improvements, demonstrate novel modes of operation which enhance device functionality, and develop and implement protocols for the entanglement of remote microwave qubits.
We continue to develop and improve a complex optical and electrical measurement system required to accurately characterize the quantum operation of transducer devices while preserving fragile quantum states. We use an optical-access, dry dilution refrigerator to create the millikelvin environment required to operate superconducting microwave circuitry and limit thermal occupation of mechanical modes. The Transducer Design and Fabrication Project is developing a vibrating membrane transducer for which long- and short-term measurement stability are critical to accurate device characterization. On the optical side we are developing monolithic device structures, vibration isolation stages, and fast optical cavity locking techniques. On the electrical side we are implementing microwave pumps with ultra-low phase noise while utilizing NIST-built traveling wave parametric amplifiers (TWPAs) with low added noise for low uncertainty device measurements.
The performance of transducer prototypes today is limited by added classical noise and low throughput (bandwidth x efficiency x duty cycle). Beyond new transducer designs, novel operating approaches such as multiplexing can be used to increase throughput while quantum feedforward protocols and coding can reduce correlated classical noise. We are also developing systems engineering approaches for the characterization of transducers with Gaussian channel tomography.
Creating entanglement between distant microwave qubits, whether located on separate chips within a single cryostat or between two cryostats, requires implementing a quantum protocol like teleportation. We are demonstrating a hybrid protocol which interacts a continuous variables, squeezed, entanglement resource with discrete variables, microwave qubit states. To handle sources of errors, our protocol is distillation-ready with simple Gaussian operations. Our effort also leverages transmon qubit circuits being developed at NIST by the Scalable Quantum Computing Group.
The Quantum Transducer Characterization and Protocols Project will:
• Characterize novel microwave-to-optical transducer devices being developed at NIST
• Demonstrate operational protocols to increase transducer throughput and lower added noise
• Develop and demonstrate remote hybrid qubit-qubit entanglement protocols.
• Develop stable optical and electrical measurement systems in a cryogenic environment
• Define operational thresholds for transducers which achieve quantum operation
The Results of this Project will Directly Impact:
• Scalable quantum computing
• Secure quantum communications
• Quantum sensing and metrology
• Quantum transducer technology
• Future quantum networking standards
• US leadership in Quantum 2.0 technologies
• US global competitiveness
• US national security
Literature References
• Entanglement Thresholds of Doubly Parametric Quantum Transducers, Curtis L. Rau, Akira Kyle, Alex Kwiatkowski, Ezad Shojaee, John D. Teufel, Konrad W. Lehnert, and Tasshi Dennis, Phys. Rev. Applied, Vol. 17, 044057, April 2022.
• Optically Distributing Remote Two-Node Microwave Entanglement Using Doubly Parametric Quantum Transducers, Akira Kyle, Curtis L. Rau, William D. Warfield, Alex Kwiatkowski, John D. Teufel, Konrad W. Lehnert, and Tasshi Dennis, Phys. Rev. Applied, Vol. 20, 014055, July 2023.
WANT TO BE INVOLVED?
There are numerous ways to contribute to this project team, which benefits from a diversity of expertise and varied levels of prior experience.
The NRC Postdoctoral Program
The NRC Research Associateship Program has opportunities available for research related to this project (eligibility requirements include US Citizenship). Application cycles are in January and August, and it is recommended that you contact us well in advance of this deadline.
The NIST PREP Program
The NIST Professional Research Experience Program (PREP) was created at NIST-Boulder in 1991 and is designed to provide valuable laboratory experience and financial assistance to undergraduates, graduate students, postdocs, and professional researchers. The program is intended to assure the continued growth and progress of a highly skilled science, technology, engineering, and math (STEM) workforce in the United States.
The NIST SURF Program
The NIST-Boulder Summer Undergraduate Research Fellowship (SURF) program provides summer research opportunities for undergraduate researchers during an 11-week program. Students work alongside NIST scientists and will have their own research projects to complete. Student applications are submitted in February.
Research Collaborations
Collaborations are available to US and international citizens as well as various government agencies.
If you are interested or have any questions, please contact the group leader, tasshi.dennis [at] nist.gov (Tasshi Dennis).