Repetitive quantum non-demolition measurement and soft decoding of a silicon spin qubit

Abstract

Quantum error correction is of crucial importance for fault-tolerant quantum computers. As an essential step towards the implementation of quantum error-correcting codes, quantum non-demolition (QND) measurements are needed to efficiently detect the state of a logical qubit without destroying it. Here we implement QND measurements in a Si/SiGe two-qubit system, with one qubit serving as the logical qubit and the other serving as the ancilla. Making use of a two-qubit controlled-rotation gate, the state of the logical qubit is mapped onto the ancilla, followed by a destructive readout of the ancilla. Repeating this procedure enhances the logical readout fidelity from $75.5\pm 0.3\%$ to $94.5\pm 0.2\%$ after 15 ancilla readouts. In addition, we compare the conventional thresholding method with an improved signal processing method called soft decoding that makes use of analog information in the readout signal to better estimate the state of the logical qubit. We demonstrate that soft decoding leads to a significant reduction in the required number of repetitions when the readout errors become limited by Gaussian noise, for instance in the case of readouts with a low signal-to-noise ratio. These results pave the way for the implementation of quantum error correction with spin qubits in silicon.

References in corpus (18)

• Surface codes: Towards practical large-scale quantum computation
• Single-shot read-out of an individual electron spin in a quantum dot
• High-fidelity projective readout of a solid-state spin quantum register
• High-fidelity preparation, gates, memory and readout of a trapped-ion quantum bit
• Electrically driven single electron spin resonance in a slanting Zeeman field
• Quantum sensing with arbitrary frequency resolution
• Rapid high-fidelity gate-based spin read-out in silicon
• Fault-tolerant bosonic quantum error correction with the surface-GKP code
• Protocols for optimal readout of qubits using a continuous quantum nondemolition measurement
• Analog quantum error correction with encoding a qubit into an oscillator
• High-fidelity measurement of qubits encoded in multilevel superconducting circuits
• Quantum nondemolition measurement of an electron spin qubit
• Measurement efficiency and n-shot read out of spin qubits
• Non-destructive measurement of electron spins in a quantum dot
• Soft Decoding of a Qubit Readout Apparatus
• Data processing over single-port homodyne detection to realize super-resolution and super-sensitivity
• Optimal signal processing for continuous qubit readout
• Repetitive Readout Enhanced by Machine Learning

Cited by in corpus (31)

• Universal control of a six-qubit quantum processor in silicon
• CMOS-based cryogenic control of silicon quantum circuits
• Review of performance metrics of spin qubits in gated semiconducting nanostructures
• Quantum tomography of an entangled three-spin state in silicon
• Spiderweb array: A sparse spin-qubit array
• Entanglement-Based Quantum Information Technology
• Hole spin qubits in Si FinFETs with fully tunable spin-orbit coupling and sweet spots for charge noise
• Low overhead fault-tolerant quantum error correction with the surface-GKP code
• Conditional quantum operation of two exchange-coupled single-donor spin qubits in a MOS-compatible silicon device
• Repetitive readout and real-time control of nuclear spin qubits in ${}^{171}$Yb atoms
• Rapid single-shot parity spin readout in a silicon double quantum dot with fidelity exceeding 99 %
• Single-shot readout of a driven hybrid qubit in a GaAs double quantum dot
• Reducing the error rate of a superconducting logical qubit using analog readout information
• Beating the thermal limit of qubit initialization with a Bayesian Maxwell's demon
• Tomography of entangling two-qubit logic operations in exchange-coupled donor electron spin qubits
• Spin-Valley Qubit Dynamics In Exchange Coupled Silicon Quantum Dots
• Feedback-based active reset of a spin qubit in silicon
• Parallel tomography of quantum non-demolition measurements in multi-qubit devices
• Generalized figure of merit for qubit readout
• Complete physical characterization of QND measurements via tomography
• Error channels in quantum nondemolition measurements on spin systems
• Quantum non-demolition measurement based on an SU(1,1)-SU(2)-concatenated atom-light hybrid interferometer
• Quantum Non-Demolition Measurement on the Spin Precession of Laser-Trapped ${}^{171}$Yb Atoms
• Detection of charge states of an InAs nanowire triple quantum dot with an integrated nanowire charge sensor
• Characterization of coherent errors in gate layers with robustness to Pauli noise
• Flying-cat parity checks for quantum error correction
• GHz operation of a quantum point contact using stub impedance matching circuit
• Spin-qubit readout analysis based on a hidden Markov model
• Andreev qubit readout from dynamic interference supercurrent
• Maximizing the nondemolition nature of a quantum measurement via an adaptive readout protocol
• Soft information decoding with superconducting qubits