A practical quantum computer requires 5 key elements:
- A qubit technology: A well-understood and scalable qubit technology is needed to build arrays of qubits that can be programmed, readout, and that can interact with each other.
- A way to initialize each qubit: There needs to be a mechanism to initialize qubits to a known state and have the initialization as reliable as possible.
- Fast operations with respect to the qubit coherence time: Quantum gates have to be fast enough so the computation is complete before qubits lose their state.
- A universal set of quantum gates: A universal set of quantum gates permits arbitrary computation.
- A method of reading the state of qubits: As with any computer, measuring the results is required. In a quantum computer, the readout circuit is used to determine the result of a computation, or in other words, the state of each qubit.
A readout circuit is an essential part of a quantum computer since it is responsible to obtaining the final computation results. The readout circuit has to introduce very low noise to the already fragile measurements. As such, the readout circuitry in typically cooled by very low cryogenic temperatures. Beside the cryogenic cooling, the low-noise amplifiers in the readout circuit should be noise matched to further reduce their noise contribution. Such matching, requires the knowledge of cryogenic noise parameters, which can be measured with NoiseTech’s cryogenic impedance generators.
The following video discusses various useful instruments for developing quantum computers. The part of particular interest starts at 25:20 where cryogenic noise parameter measurements with C-IG0160CT are discussed.