Millimeter waves read out a qubit with 99% accuracy

Akash V. Dixit and colleagues from the National Institute of Standards and Technology and the University of Colorado Boulder have demonstrated a qubit readout with over 99% accuracy without relying on a quantum limited amplifier. The team achieved this performance by using millimeter waves to interact with a transmon qubit within a circuit quantum electrodynamic system, coupled at a rate of 230 MHz. A key to their success was suppressing unwanted state transitions by maintaining a large frequency separation, where ωr/ωq > 10, and using up to 1,000 drive photons. This approach offers a path toward simpler and potentially less expensive quantum computing infrastructure. This level of accuracy demonstrates a potential simplification of quantum computing infrastructure, reducing the need for complex and costly amplification systems. Researchers envision this technology as a key component in future hybrid quantum systems,…