Donor-based spin qubit offers a promising silicon quantum computing route for building large-scale qubit arrays, attributed to its long coherence time and advancements in nanoscale donor placement. However, the state-of-the-art device designs face scalability challenges, notably in achieving tunable two-qubit coupling and ensuring qubit addressability. Here, we propose a surface-code-compatible architecture, where each module has both tunable two-qubit gates and addressable single-qubit gates by introducing only a single extra donor in a pair of donors. We found that to compromise between the requirement of tunability and that of addressability, an asymmetric scheme is necessary. In this scheme, the introduced extra donor is strongly tunnel-coupled to one of the donor spin qubits for addressable single-qubit operation, while being more weakly coupled to the other to ensure the turning on and off of the two-qubit operation. The fidelity of single-qubit and two-qubit gates can exceed the fault-tolerant threshold in our design. Additionally, the asymmetric scheme effectively mitigates valley oscillations, allowing for engineering precision tolerances up to a few nanometers. Thus, our proposed scheme presents a promising prototype for large-scale, fault-tolerant, donor-based spin quantum processors.Donor-based spin qubit offers a promising silicon quantum computing route for building large-scale qubit arrays, attributed to its long coherence time and advancements in nanoscale donor placement. However, the state-of-the-art device designs face scalability challenges, notably in achieving tunable two-qubit coupling and ensuring qubit addressability. Here, we propose a surface-code-compatible architecture, where each module has both tunable two-qubit gates and addressable single-qubit gates by introducing only a single extra donor in a pair of donors. We found that to compromise between the requirement of tunability and that of addressability, an asymmetric scheme is necessary. In this scheme, the introduced extra donor is strongly tunnel-coupled to one of the donor spin qubits for addressable single-qubit operation, while being more weakly coupled to the other to ensure the turning on and off of the two-qubit operation. The fidelity of single-qubit and two-qubit gates can exceed the fault-tolerant threshold in our design. Additionally, the asymmetric scheme effectively mitigates valley oscillations, allowing for engineering precision tolerances up to a few nanometers. Thus, our proposed scheme presents a promising prototype for large-scale, fault-tolerant, donor-based spin quantum processors.

arXiv:2412.20055Dec 28, 20240 citations

Quantum thermodynamics for quantum computing

Machiel Blok, Gabriel Teixeira Landi

Nature PhysicsJan 27, 20259 citations

Thermodynamic And Quantum Constraints On Scalable Quantum Computing

Rowan Brad Quni-Gudzinas

Jan 1, 20250 citations

Industry-compatible silicon spin-qubit unit cells exceeding 99% fidelity

Paul Steinacker, Nard Dumoulin Stuyck, Wee Han Lim +26 more

Abstract Among the many types of qubit presently being investigated for a future quantum computer, silicon spin qubits with millions of qubits on a single chip are uniquely positioned to enable quantum computing. However, it has not been clear whether the outstanding high-fidelity operations and long coherence times shown by silicon spin qubits fabricated in academic settings 1–8 can be reliably reproduced when the qubits are manufactured in a semiconductor foundry 9–11 . Here we show precise qubit operation of silicon two-qubit devices made with standard semiconductor tooling in a 300-mm foundry environment. Of the key metrics, single- and two-qubit control fidelities exceed 99% for all four devices, and the state preparation and measurement fidelities reach up to 99.9%, as evidenced by gate set tomography. We report spin lifetime and coherence up to T 1 = 9.5 s, ${T}_{2}^{* }=40.6\,{\rm{\mu }}{\rm{s}}$ T 2 * = 40.6 μ s and ${T}_{2}^{{\rm{Hahn}}}=1.9\,{\rm{ms}}$ T 2 Hahn = 1.9 ms . We determine that residual nuclear spin-carrying isotopes contribute substantially to operational errors, identifying further isotopic purification as a clear pathway to even higher performance.Abstract Among the many types of qubit presently being investigated for a future quantum computer, silicon spin qubits with millions of qubits on a single chip are uniquely positioned to enable quantum computing. However, it has not been clear whether the outstanding high-fidelity operations and long coherence times shown by silicon spin qubits fabricated in academic settings 1–8 can be reliably reproduced when the qubits are manufactured in a semiconductor foundry 9–11 . Here we show precise qubit operation of silicon two-qubit devices made with standard semiconductor tooling in a 300-mm foundry environment. Of the key metrics, single- and two-qubit control fidelities exceed 99% for all four devices, and the state preparation and measurement fidelities reach up to 99.9%, as evidenced by gate set tomography. We report spin lifetime and coherence up to T 1 = 9.5 s, $${T}_{2}^{* }=40.6\,{\rm{\mu }}{\rm{s}}$$ T 2 * = 40.6 μ s and $${T}_{2}^{{\rm{Hahn}}}=1.9\,{\rm{ms}}$$ T 2 Hahn = 1.9 ms . We determine that residual nuclear spin-carrying isotopes contribute substantially to operational errors, identifying further isotopic purification as a clear pathway to even higher performance.

arXiv:2410.15590NatureSep 24, 202558 citations

Quantum Computation on a Silicon Chip

Xiao, Yunfeng Yunfeng, Han +3 more

量子光学学报Jan 1, 20060 citations

Silicon Quantum Computer

Kohei M. Itoh

Our progress towards realization of the all‐silicon solid‐state NMR quantum computer [PRL, 89, 017901 (2002) and revised version] is reported. We show experimentally that the phase memory time TM (or phase decoherence time T2) of 29Si nuclear spins in single‐crystal Si at room temperature can be extended up to 25 s (and possibly more) using RF decoupling techniques [quant‐ph/0309164 (2003)]. A simple estimate shows that a T2 of 25 s will allow for 106 single‐qubit and 104 two‐qubit operations, by far the largest number of operations possible among existing solid‐state quantum computer schemes. Recent progress in materials science needed for the realization of the all‐silicon quantum computer is also discussed.Our progress towards realization of the all‐silicon solid‐state NMR quantum computer [PRL, 89, 017901 (2002) and revised version] is reported. We show experimentally that the phase memory time TM (or phase decoherence time T2) of 29Si nuclear spins in single‐crystal Si at room temperature can be extended up to 25 s (and possibly more) using RF decoupling techniques [quant‐ph/0309164 (2003)]. A simple estimate shows that a T2 of 25 s will allow for 106 single‐qubit and 104 two‐qubit operations, by far the largest number of operations possible among existing solid‐state quantum computer schemes. Recent progress in materials science needed for the realization of the all‐silicon quantum computer is also discussed.

AIP conference proceedingsJan 1, 20050 citations

{T}_{2}^{* }=40.6\,{\rm{\mu }}{\rm{s}}

T 2 * = 40.6 μ s and

{T}_{2}^{{\rm{Hahn}}}=1.9\,{\rm{ms}}

T 2 Hahn = 1.9 ms . We determine that residual nuclear spin-carrying isotopes contribute substantially to operational errors, identifying further isotopic purification as a clear pathway to even higher performance.