Spin-Based Quantum Computing
Spin-based quantum computing is a leading technology for the realization of scalable quantum computers. Semiconductor Quantum Dots (QD) are used to trap individual charges and the associated spins, which are then used as qubits. The Zurich Instruments Quantum Computing Control System (QCCS) provides all the key tools for spin qubit characterization, control and readout, providing a low-noise and scalable solution that improves setup reliability and simplifies setup control.
Single spins are confined in semiconductors quantum dots. Metallic gates define them and control the relative couplings. A large quantum dot is used as a charge sensor for the smaller ones which are serving as qubits. Single qubit operations are induced through an oscillating magnetic field coupled to the qubits through microwave strip lines. Two qubits gates can be realized with fast pulses on those metallic gates which are close to two quantum dots.
The QCCS can be used for all critical characterization steps and for the operation of a spin qubit system.
The MFLI Lock-in amplifier is used for quantum dot characterization. The integrated low noise current amplifier is able to amplify the tiny current flowing through a typical QD and the multiple oscillators are set at different frequencies in order to simultaneously acquire DC conductance, low-frequency conductance and gate trans-impedance. The digitizer function can be used to acquire fast current traces to perform single-shot spin readout.
Fast multiplexed qubit control
The HDAWG generates the fast pulses for the metallic gates which are used to control the QD energy levels, couplings and drive the two-qubit gates. To counteract the effect of the cross-coupling, additional pulses are applied to multiple gates. The HDAWG is able to modulate the microwave source in order to produce single qubit gates. Different qubits can be addressed with frequency multiplexing. A Single-Sideband modulation scheme, in conjunction with the internal oscillators, is used to suppress unwanted images and facilitate a clean spectrum.
The spin-readout speed is greatly improved when performed at high frequency with RF reflectometry. The UHFLI Lock-in amplifier generates the probe RF readout tone and acquires the reflected response of the sensing QD to perform fast and high-fidelity single-shot spin readout. Up to eight sensing dots can be multiplexed and read simultaneously. The magnitude or the phase of the demodulated signals are a measure of the complex impedance of the charge sensor, from which the qubit's state can be measured.
The Benefits of Choosing Zurich Instruments
The QCCS provide all the critical components to characterize and control a complex spin qubit computer.
- Low setup complexity and maintenance effort thanks to a high level of integration:
- Current amplifier, multimeter, lock-in amplifier and digitizer all in a single unit.
- Reflectometry readout with unified signal generation and detection without the need for external analog up-/down-conversion.
- Reduced need for isolation and filtering leads to low power dissipation at the input connectors.
- Accurate spin control and enhanced fidelity, also for fast qubits, thanks to the fast and low-noise HDAWG outputs.
- Advanced and complex experiments with the real-time sequencer.
- Clear pathway to larger numbers of qubits: control many multiplexed qubits with the internal oscillators and the large output bandwidth.
- Fast integration into your control environment and existing setup: powerful LabOne APIs with drivers for QCoDeS and Labber.
The QCCS is a future-proof investment that optimizes your workflows and setup performance.
- Hanson, R. et al. Spins in few-electron quantum dots. Rev. Mod. Phys. 79, 1217 (2007)
- Crippa, A. et al. Gate-reflectometry dispersive readout and coherent control of a spin qubit in silicon. Nat. Commun. 10, 2776 (2019)
- Vukušić, L. et al. Single-Shot Readout of Hole Spins in Ge. Nano Lett. 18, 7141-7145 (2018)
- Crippa, A. et al. Level Spectrum and Charge Relaxation in a Silicon Double Quantum Dot Probed by Dual-Gate Reflectometry. Nano Lett. 17, 1001-1006 (2017)
- RF reflectometry measurements of quantum dots
- Generation of single-sideband modulation by arbitrary waveform generators
- Output low-frequency sinusoidal signal on the AUX output of the MFLI
- Demodulating down to DC