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Molecular qubits are an emerging platform in quantum information science (QIS) due to the unmatched structural control that chemical design and synthesis provide compared to other leading qubit technologies. This theoretical study investigates pulse sequence protocols for spin-correlated radical pairs (SCRPs), which are important molecular spin qubit pair (SQP) candidates. Here, we introduce improved microwave pulse protocols for enhancing the execution times of quantum logic gates based on SQPs. Signi ficantly, this study demonstrates that the proposed pulse sequences selectively remove certain contributions from nuclear spin effects on spin dynamics, which are a common source of decoherence. Additionally, we have analyzed the factors that control the fidelity of the SQP spin state following application of the CNOT gate. It was found that higher magnetic fi elds introduce a high frequency oscillation in the fidelity. Thereupon, it is suggested that further research should be geared towards executing quantum gates at lower magnetic field values. In addition, an absolute bound of the fidelity outcome due to decoherence is determined, which clearly identifies the important factors that control gate execution. Finally, examples of the application of these pulse sequences to SQPs are described.
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Quantum control of spin qubits using nanomagnets
Abstract Single-qubit gates are essential components of a universal quantum computer. Without selective addressing of individual qubits, scalable implementation of quantum algorithms is extremely challenging. When the qubits are discrete points or regions on a lattice, selectively addressing magnetic spin qubits at the nanoscale remains a challenge due to the difficulty of localizing and confining a classical divergence-free field to a small volume of space. Herein we propose a technique for addressing spin qubits using voltage-control of nanoscale magnetism, exemplified by the use of voltage control of magnetic anisotropy. We show that by tuning the frequency of the nanomagnet’s electric field drive to the Larmor frequency of the spins confined to a nanoscale volume, and by modulating the phase of the drive, single-qubit quantum gates with fidelities approaching those for fault-tolerant quantum computing can be implemented. Such single-qubit gate operations require only tens of femto-Joules per gate operation and have lossless, purely magnetic field control. Their physical realization is also straightforward using foundry manufacturing techniques.
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- PAR ID:
- 10379913
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Communications Physics
- Volume:
- 5
- Issue:
- 1
- ISSN:
- 2399-3650
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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