Dephasing of Exchange‐Coupled Spins in Quantum Dots for Quantum Computing

Abstract

A spin qubit in semiconductor quantum dots holds promise for quantum information processing for scalability and long coherence time. An important semiconductor qubit system is a double quantum dot trapping two electrons or holes, whose spin states encode either a singlet–triplet qubit or two single‐spin qubits coupled by exchange interaction. In this article, progress on the spin dephasing of two exchange‐coupled spins in a double quantum dot is reported. First, the schemes of two‐qubit gates and qubit encodings in gate‐defined quantum dots or donor atoms based on the exchange interaction are discussed. Then, the progress on spin dephasing of a singlet–triplet qubit or a two‐qubit gate is reported. The methods of suppressing spin dephasing are further discussed. The understanding of the spin dephasing may provide insights into the realization of high‐fidelity quantum gates for spin‐based quantum computing.

Enhanced Coherence by Coupling Spins through a Delocalized π-System: Vanadyl Porphyrin Dimers

“…Si quantum dots and Ti atoms, show that exchange coupled spins via quantum mediators can suppress decoherence. [15][16][17][18][19][20] Observing such effects in π-conjugated molecules would lead to better designs for functional magnetic materials. 21,22 With the purpose of exploring this issue, molecular magnets have been immobilized onto or into carbon nanotubes [23][24][25][26][27][28][29] and π-conjugated backbones have been combined with magnetic centers, such as open-shell graphenoids [30][31][32] or graphene nanoribbons.…”