Making Bigger Quantum Computers - How do we handle more qubits Problem: There is not enough room in the refrigerator! - QCs mostly need to operate inside cryogenic environments - Electronics needed for control and read out don't work at some temperatures. So the circuits must reside outside those refrigerators - Today, for sub 100 qubit systems, there is enough of space for specialised cooling to make that connection. Though for future 1 million qubit systems there won't be. - Creating a need for ultralow-power control chips, that can operate inside the refrigerator ### CryoCMOS - Intel's Horse Ridge (Jim Clarke) - works at 4k - translates quantum-computer instructions into basic qubit operations, which it delivers to the processor as microwave signals. - chip built using 22-nanometer FinFET manufacturing process - transistors that make up the control circuitry needed substantial reengineering - Google - MSFT ### Microrelays - micrometer-scale electromechanical relays as ultralow-power alternatives to transistors. - University of California - https://spectrum.ieee.org/tech-talk/semiconductors/devices/micrometerscale-mechanical-switches-work-at-just-50-millivolts ### Single-flux quantum logic - [Hypres](https://www.hypres.com/), in Elmsford, N.Y., has been commercializing cryogenic ICs for several years. - Steered it's rapid single-flux quantum (RSFQ) logic tech into the realm of quantum computing, by spinning out [Seeqc](https://seeqc.com/) - In RSFQ and its quantum version, SFQuClass logic, quantized pulses of voltage are blocked, passed, or routed by Josephson junctions, the same type of superconducting devices that make up most of today’s quantum computer chips. - [[Seeqc]] is now designing an entire system using the technology: a digital-control, error-correction, and readout chip designed to work at 3 to 4 K and a separate chip designed to work at 20 millikelvins to interface with the quantum processor. ### Weyl semimetals - Lund University & IBM research Zurich - Weyl semimetal amplifier that they say could bring readout electronics closer to the qubits. - materials, such as tungsten diphosphide, exhibit extremely strong, temperature-dependent magnetoresistance when chilled to below about 50 K. - The device they simulated has a gate electrode that produces a magnetic field inside the Weyl semimetal, causing its resistance to go from tiny to huge in a matter of picoseconds. - onnecting the input from a qubit to the device could make a high-gain amplifier that dissipates a mere 40 microwatts. That could be low enough for the amplifier to live in the part of the fridge close to where the qubits themselves reside. #quantum