QphoX and Rigetti Announce New Optical Readout Technique for Superconducting Qubits
Collaborative research from QphoX and Rigetti demonstrates the ability to readout superconducting qubits with an optical transducer. This approach could have benefits in building scalable quantum computers as it could be a more compact, modular, approach for measuring qubit performance in quantum computing systems that rely on microwave amplification.

Delft, the Netherlands and Berkeley, USA -- QphoX B.V., a quantum technology startup that is developing an optical readout solution for microwave-based quantum systems, and Rigetti Computing, Inc. (Nasdaq: RGTI), a pioneer in full-stack quantum-classical computing, today announce that they have demonstrated the ability to readout superconducting qubits with an optical transducer. Current qubit readout techniques used by superconducting quantum computer systems in cryogenic environments can be resource intensive from a thermal and power usage perspective. This technique could have benefits in designing and building scalable quantum computers as it is a more compact, modular, heat-efficient approach to conducting qubit readout.

The team's initial proof of concept using QphoX's optical transducer connected to a Rigetti superconducting transmon qubit achieved an optical readout with a fidelity exceeding 99%. This demonstration marks an important milestone in Rigetti and QphoX's collaboration to evaluate the potential of applying microwave-to-optical conversion to multi-qubit readout in superconducting qubit devices.

New research recently released by the Rigetti and QphoX teams shows, for the first time, the results of qubit readout (determining the qubit's state) using a fully integrated transducer that can scale alongside next generation quantum computers.

"Exploring new approaches to qubit signal processing as we plan to scale to even larger qubit counts is a valuable undertaking and we are thrilled to be able to benefit from QphoX's expertise in optical readout technology," said Dr. Subodh Kulkarni, Rigetti CEO.

"By leveraging our unique microwave to optical quantum conversion technology, we're able to minimize the spatial and heat load constraints placed on the cryostat in which modern quantum processors are housed, allowing us to support scaling of these systems to commercially interesting numbers of qubits. Our demonstration of this technology with a Rigetti quantum integrated circuit (QuIC) device, highlights the maturity and potential of our technology and marks a milestone in our partnership" said Dr. Robert Stockill, CTO and Co-Founder at QphoX.

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About Rigetti
Rigetti is a pioneer in full-stack quantum computing. The company has operated quantum computers over the cloud since 2017 and serves global enterprise, government, and research clients through its Rigetti Quantum Cloud Services platform. Rigetti's proprietary quantum-classical infrastructure provides high performance integration with public and private clouds for practical quantum computing. Rigetti has developed the industry's first multi-chip quantum processor for scalable quantum computing systems. The company designs and manufactures its chips in-house at Fab-1, the industry's first dedicated and integrated quantum device manufacturing facility. Learn more at www.rigetti.com.

About QphoX
QphoX is developing the world's first Quantum Modem™, a breakthrough device that will allow the quantum computing industry to scale through connectivity and parallelization and unlock the potential of the Quantum Internet. QphoX also provides optical readout and control solutions for quantum processors to address intermediate scaling challenges within single cryostats. The company's first product, a cryogenic switch controller for actuation of microwave switches, has recently been released. QphoX is based in Delft, the Netherlands. See www.qphox.eu for more information.

12 October, 2023