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Abstract
Quantum computation relies on accurate measurements of qubits not only for reading the output of the calculation, but also to perform error correction. Most proposed scalable silicon architectures utilize Pauli blockade of triplet states for spintocharge conversion. In recent experiments there have been instances when instead of conventional triplet blockade readout, Pauli blockade is sustained only between parallel spin configurations, with vertical bar T0 > relaxing quickly to the singlet state and leaving vertical bar T+> and vertical bar T> states blockadedwhich we call parity readout. Both types of blockade can be used for readout in quantum computing, but it is crucial to maximize the fidelity and understand in which regime the system operates. We devise and perform an experiment in which the crossover between parity and singlettriplet readout can be identified by investigating the underlying physics of the vertical bar T0 > relaxation rate. This rate is tunable over 4 orders of magnitude by controlling the Zeeman energy difference between the dots induced by spinorbit coupling, which in turn depends on the direction of the applied magnetic field. We suggest a theoretical model incorporating charge noise and relaxation effects that explains quantitatively our results. Investigating the model both analytically and numerically, we identify strategies to obtain on demand either singlettriplet or parity readout consistently across large arrays of dots. We also discuss how parity readout can be used to perform full twoqubit state tomography and its impact on quantum errordetection schemes in largescale silicon quantum computers.
Original language  English 

Article number  010303 
Number of pages  12 
Journal  PRX Quantum 
Volume  2 
Issue number  1 
DOIs  
Publication status  Published  7 Jan 2021 
MoE publication type  A1 Journal articlerefereed 
Keywords
 ELECTRONSPIN
 COHERENCE
 FIDELITY
 NOISE
 QUBIT
 GATE
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CRYOMET: Fast Cryogenic Microwave Photon Power Metrology in Superconducting Quantum Circuits (CRYOMET)
Tan, K., Zamora Zamora, R. & Sevriuk, V.
01/09/2018 → 31/08/2022
Project: Academy of Finland: Other research funding

SPINBUS: Quantum Bus for a Quantum Computer Based on Spins in Silicon
01/09/2017 → 31/08/2022
Project: Academy of Finland: Other research funding

SPINBUS: Quantum Bus for a Quantum Computer Based on Spins in Silicon (SPINBUS)
Tan, K., Kalliokoski, M., Catto, G., Keränen, A., Zamora Zamora, R., Sevriuk, V., Jenei, M. & Kokkoniemi, R.
01/09/2017 → 31/08/2020
Project: Academy of Finland: Other research funding