Josephson parametric amplifier offers increased qubit frequency in quantum computing

In quantum computing, conventional superconducting qubits operate at frequencies less than 10 gigahertz and at temperatures less than 20 millikelvin. Increasing this temperature to 1 kelvin would make it easier to scale. However, the thermal noise at 1 kelvin causes decoherence at low frequencies.

Thus, operating superconducting qubits at higher temperatures requires higher operation frequencies to suppress noise from thermal photons. In these systems, Josephson parametric amplifiers (JPAs) are a promising candidate for obtaining high-fidelity readout of qubits at higher frequencies.

Hao et al. designed and demonstrated a wireless Josephson parametric amplifier (WJPA) operating above 20 gigahertz. Using a wireless design allowed the team to mitigate issues at higher frequencies, such as losses and impedance mismatches. They measured the amplifier gain, bandwidth and compression power and verified its low noise performance by both classical microwave engineering measurements and with a superconducting qubit.

“The main impact of the work is to give a positive example that such JPAs are operable at high frequency and can be nearly quantum-limited,” said author Shyam Shankar. “The design is agnostic to the junction used so Josephson elements made with niobium, niobium nitride, or other materials could be used in this way to make high-temperature, high-frequency JPAs.”

With more than 20 dB of gain, the group’s JPA can be tuned from 21 to 23.5 gigahertz with only two photons of added noise, close to the standard quantum limit of one-half photon.

The group next looks to measure a qubit with this amplifier and demonstrate high-fidelity qubit readout.

Source: “Wireless Josephson amplifier above 20 GHz,” by Zhuoqun Hao, Josiah Cochran, Yao Chun Chang, Haley Cole, and Shyam Shankar, Applied Physics Letters (2026). The article can be accessed at https://doi.org/10.1063/5.0300910 .