Singlet-only Always-on Gapless Exchange Qubits with Baseband Control
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arXiv
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| Hauptverfasser: | , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866918135906435072 |
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| author | Foulk, Nathan L. Hoffman, Silas Laubscher, Katharina Sarma, Sankar Das |
| author_facet | Foulk, Nathan L. Hoffman, Silas Laubscher, Katharina Sarma, Sankar Das |
| contents | We propose a singlet-only always-on gapless exchange (SAGE) spin qubit that encodes a single qubit in the spins of four electrons while allowing universal baseband control. While conventional exchange-only qubits suffer from magnetic-field-gradient-induced leakage and coherent errors, for instance due to local nuclear environments and variations in the $g$-factor, the SAGE qubit subspace is protected from coherent errors due to local magnetic field gradients and leakage out of the computational subspace is energetically suppressed due to the exchange interactions between electrons being always-on. Consequently, we find that when magnetic gradient noise dominates over charge noise, coherence times and single-qubit gate infidelities of the SAGE qubit improve by an order of magnitude compared to conventional exchange-only qubits. Moreover, using realistic parameters, two-qubit gates can be performed with a single interqubit exchange pulse with times comparable in duration to conventional exchange-only qubits but with a significantly simplified pulse sequence. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_18589 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Singlet-only Always-on Gapless Exchange Qubits with Baseband Control Foulk, Nathan L. Hoffman, Silas Laubscher, Katharina Sarma, Sankar Das Quantum Physics Mesoscale and Nanoscale Physics We propose a singlet-only always-on gapless exchange (SAGE) spin qubit that encodes a single qubit in the spins of four electrons while allowing universal baseband control. While conventional exchange-only qubits suffer from magnetic-field-gradient-induced leakage and coherent errors, for instance due to local nuclear environments and variations in the $g$-factor, the SAGE qubit subspace is protected from coherent errors due to local magnetic field gradients and leakage out of the computational subspace is energetically suppressed due to the exchange interactions between electrons being always-on. Consequently, we find that when magnetic gradient noise dominates over charge noise, coherence times and single-qubit gate infidelities of the SAGE qubit improve by an order of magnitude compared to conventional exchange-only qubits. Moreover, using realistic parameters, two-qubit gates can be performed with a single interqubit exchange pulse with times comparable in duration to conventional exchange-only qubits but with a significantly simplified pulse sequence. |
| title | Singlet-only Always-on Gapless Exchange Qubits with Baseband Control |
| topic | Quantum Physics Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2501.18589 |