scholarly journals Protecting quantum entanglement from leakage and qubit errors via repetitive parity measurements

2020 ◽  
Vol 6 (12) ◽  
pp. eaay3050 ◽  
Author(s):  
C. C. Bultink ◽  
T. E. O’Brien ◽  
R. Vollmer ◽  
N. Muthusubramanian ◽  
M. W. Beekman ◽  
...  
Keyword(s):  
Large Scale ◽  
Markov Models ◽  
Hidden Markov ◽  
Quantum Error Correction ◽  
Trapped Ions ◽  
Entangled States ◽  
Computationally Efficient ◽  
Physical Systems ◽  
Superconducting Circuits ◽  
Quantum Error

Protecting quantum information from errors is essential for large-scale quantum computation. Quantum error correction (QEC) encodes information in entangled states of many qubits and performs parity measurements to identify errors without destroying the encoded information. However, traditional QEC cannot handle leakage from the qubit computational space. Leakage affects leading experimental platforms, based on trapped ions and superconducting circuits, which use effective qubits within many-level physical systems. We investigate how two-transmon entangled states evolve under repeated parity measurements and demonstrate the use of hidden Markov models to detect leakage using only the record of parity measurement outcomes required for QEC. We show the stabilization of Bell states over up to 26 parity measurements by mitigating leakage using postselection and correcting qubit errors using Pauli-frame transformations. Our leakage identification method is computationally efficient and thus compatible with real-time leakage tracking and correction in larger quantum processors.

scholarly journals Quantum error-correction codes and absolutely maximally entangled states

2020 ◽  
Vol 101 (4) ◽  
Author(s):  
Paweł Mazurek ◽  
Máté Farkas ◽  
Andrzej Grudka ◽  
Michał Horodecki ◽  
Michał Studziński
Keyword(s):  
Error Correction ◽  
Quantum Error Correction ◽  
Entangled States ◽  
Error Correction Codes ◽  
Maximally Entangled States ◽  
Quantum Error Correction Codes ◽  
Quantum Error

scholarly journals A Spatial-Contextual Indoor Trajectory Prediction Approach via Hidden Markov Models

2022 ◽  
Vol 2022 ◽  
pp. 1-13
Author(s):  
Peng Wang ◽  
Jing Yang ◽  
Jianpei Zhang
Keyword(s):  
Large Scale ◽  
Markov Models ◽  
Hidden Markov ◽  
Shopping Mall ◽  
Prediction Problem ◽  
Unified Framework ◽  
Trajectory Prediction ◽  
Indoor Space ◽  
Prediction Approach ◽  
Moving Patterns

Unlike outdoor trajectory prediction that has been studied many years, predicting the movement of a large number of users in indoor space like shopping mall has just been a hot and challenging issue due to the ubiquitous emerging of mobile devices and free Wi-Fi services in shopping centers in recent years. Aimed at solving the indoor trajectory prediction problem, in this paper, a hybrid method based on Hidden Markov approach is proposed. The proposed approach clusters Wi-Fi access points according to their similarities first; then, a frequent subtrajectory based HMM which captures the moving patterns of users has been investigated. In addition, we assume that a customer’s visiting history has certain patterns; thus, we integrate trajectory prediction with shop category prediction into a unified framework which further improves the predicting ability. Comprehensive performance evaluation using a large-scale real dataset collected between September 2012 and October 2013 from over 120,000 anonymized, opt-in consumers in a large shopping center in Sydney was conducted; the experimental results show that the proposed method outperforms the traditional HMM and perform well enough to be usable in practice.

scholarly journals Realization of three-qubit quantum error correction with superconducting circuits

Nature ◽  
2012 ◽  
Vol 482 (7385) ◽  
pp. 382-385 ◽  
Author(s):  
M. D. Reed ◽  
L. DiCarlo ◽  
S. E. Nigg ◽  
L. Sun ◽  
L. Frunzio ◽  
...  
Keyword(s):  
Error Correction ◽  
Quantum Error Correction ◽  
Superconducting Circuits ◽  
Quantum Error

scholarly journals A Silicon Surface Code Architecture Resilient Against Leakage Errors

Quantum ◽  
2019 ◽  
Vol 3 ◽  
pp. 212 ◽  
Author(s):  
Zhenyu Cai ◽  
Michael A. Fogarty ◽  
Simon Schaal ◽  
Sofia Patomäki ◽  
Simon C. Benjamin ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Error Correction ◽  
Large Scale ◽  
Building Blocks ◽  
Quantum Error Correction ◽  
Error Correction Codes ◽  
Relaxation Processes ◽  
Spin Qubits ◽  
Surface Code ◽  
Quantum Error

Spin qubits in silicon quantum dots are one of the most promising building blocks for large scale quantum computers thanks to their high qubit density and compatibility with the existing semiconductor technologies. High fidelity single-qubit gates exceeding the threshold of error correction codes like the surface code have been demonstrated, while two-qubit gates have reached 98% fidelity and are improving rapidly. However, there are other types of error --- such as charge leakage and propagation --- that may occur in quantum dot arrays and which cannot be corrected by quantum error correction codes, making them potentially damaging even when their probability is small. We propose a surface code architecture for silicon quantum dot spin qubits that is robust against leakage errors by incorporating multi-electron mediator dots. Charge leakage in the qubit dots is transferred to the mediator dots via charge relaxation processes and then removed using charge reservoirs attached to the mediators. A stabiliser-check cycle, optimised for our hardware, then removes the correlations between the residual physical errors. Through simulations we obtain the surface code threshold for the charge leakage errors and show that in our architecture the damage due to charge leakage errors is reduced to a similar level to that of the usual depolarising gate noise. Spin leakage errors in our architecture are constrained to only ancilla qubits and can be removed during quantum error correction via reinitialisations of ancillae, which ensure the robustness of our architecture against spin leakage as well. Our use of an elongated mediator dots creates spaces throughout the quantum dot array for charge reservoirs, measuring devices and control gates, providing the scalability in the design.

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