Improved quantum error correction using soft information
arXiv:2107.13589
Abstract
The typical model for measurement noise in quantum error correction is to randomly flip the binary measurement outcome. In experiments, measurements yield much richer information - e.g., continuous current values, discrete photon counts - which is then mapped into binary outcomes by discarding some of this information. In this work, we consider methods to incorporate all of this richer information, typically called soft information, into the decoding of quantum error correction codes, and in particular the surface code. We describe how to modify both the Minimum Weight Perfect Matching and Union-Find decoders to leverage soft information, and demonstrate these soft decoders outperform the standard (hard) decoders that can only access the binary measurement outcomes. Moreover, we observe that the soft decoder achieves a threshold 25\% higher than any hard decoder for phenomenological noise with Gaussian soft measurement outcomes. We also introduce a soft measurement error model with amplitude damping, in which measurement time leads to a trade-off between measurement resolution and additional disturbance of the qubits. Under this model we observe that the performance of the surface code is very sensitive to the choice of the measurement time - for a distance-19 surface code, a five-fold increase in measurement time can lead to a thousand-fold increase in logical error rate. Moreover, the measurement time that minimizes the physical error rate is distinct from the one that minimizes the logical performance, pointing to the benefits of jointly optimizing the physical and quantum error correction layers.
arXiv comment27 pages, 13 figures
References in corpus (21)
- Fault-tolerant quantum computation by anyons
- Surface codes: Towards practical large-scale quantum computation
- Cavity quantum electrodynamics for superconducting electrical circuits: an architecture for quantum computation
- Encoding a qubit in an oscillator
- Topological Quantum Distillation
- High threshold universal quantum computation on the surface code
- Confinement-Higgs transition in a disordered gauge theory and the accuracy threshold for quantum memory
- Low-distance Surface Codes under Realistic Quantum Noise
- Quantum trajectory approach to circuit QED: Quantum jumps and the Zeno effect
- Building a fault-tolerant quantum computer using concatenated cat codes
- Almost-linear time decoding algorithm for topological codes
- Dispersive Readout of a Few-Electron Double Quantum Dot with Fast rf Gate-Sensors
- Fault-tolerant bosonic quantum error correction with the surface-GKP code
- Protocols for optimal readout of qubits using a continuous quantum nondemolition measurement
- Gate-reflectometry dispersive readout and coherent control of a spin qubit in silicon
- Quantum Error Correction with the Toric-GKP Code
- Analog quantum error correction with encoding a qubit into an oscillator
- Linear-Time Maximum Likelihood Decoding of Surface Codes over the Quantum Erasure Channel
- Decoding color codes by projection onto surface codes
- The cost of universality: A comparative study of the overhead of state distillation and code switching with color codes
- Optimization of the surface code design for Majorana-based qubits