Quantum technologies at THz frequencies

Higher frequency, higher temperature

A quantum state survives only if its energy spacing is large compared with the thermal energy around it. Qubits operated at a few gigahertz therefore need dilution refrigerators at millikelvin temperatures. A quantum system with energy spacings in the terahertz range sits well above the thermal energy at 4 K, the temperature of liquid helium, where cooling power is orders of magnitude larger and the cryogenics is far simpler.

Our research targets semiconductor quantum technologies, including semiconductor qubits, at very high frequencies and at these higher temperatures. Operating faster also means that more quantum operations fit inside the time for which a qubit stays coherent.

Scaling and integration

A useful quantum processor needs many qubits, each with fast control and readout lines. We work on integrating quantum systems with high-frequency THz electronics and optoelectronics on the same chip, and on photonic packaging that brings optical signals from a fibre to the chip inside the cryostat. Delivering control signals optically avoids much of the heat load and bandwidth limit of coaxial cables.

Alongside this we are also experimenting with the development of the supporting cryogenic electronics (T-gate FETs), including high-frequency cryogenic amplifiers and controllers, that a scalable THz quantum platform requires.

Fundamental questions

Working at picosecond time scales also lets us ask how electrons interact with each other and with their environment before they have had time to relax. These ultrafast dynamics in condensed matter are both a tool for quantum technologies and a research subject in their own right.