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Bell inequality violations by partially entangled spin- pairs

Kirk McDermid

Physics Letters AAug 5, 20040 citations

Entanglement by measurement and Bell inequality violation with spins in diamond

Wolfgang Pfaff, T. H. Taminiau, Lucio Robledo +4 more

Bulletin of the American Physical SocietyMar 21, 20130 citations

Bell's inequality violation and symmetry

F. C. Khanna, A. Mann, M. Revzen +1 more

Physics Letters AFeb 1, 20023 citations

Bell inequality violation in gate-defined quantum dots

Paul Steinacker, Tuomo Tanttu, Wee Han Lim +15 more

Quantum computers leverage entanglement to achieve superior computational power. However, verifying that the entangled state does not follow the principle of local causality has proven difficult for spin qubits in gate-defined quantum dots, as it requires simultaneously high concurrence values and readout fidelities to break the classical bound imposed by Bell’s inequality. While low error rates for state preparation, control, and measurement have been independently demonstrated, a simultaneous demonstration remained challenging. We employ advanced protocols like heralded initialization and calibration via gate set tomography (GST), to push fidelities of the full 2-qubit gate set above 99%, including state preparation and measurement (SPAM). We demonstrate a 97.17% Bell state fidelity without correcting for readout errors and violate Bell’s inequality using direct parity readout with a Bell signal of S = 2.731. Our measurements exceed the classical limit even at 1.1 K or entanglement lifetimes of 100 μs. Violating Bell’s inequality in a silicon quantum dot qubit system is a key milestone, as it proves quantum entanglement, fundamental to achieving quantum advantage. Silicon-based spin qubits are promising candidates for a scalable quantum computer. Here the authors demonstrate the violation of Bell’s inequality in gate-defined quantum dots in silicon, marking a significant advancement that showcases the maturity of this platform.Quantum computers leverage entanglement to achieve superior computational power. However, verifying that the entangled state does not follow the principle of local causality has proven difficult for spin qubits in gate-defined quantum dots, as it requires simultaneously high concurrence values and readout fidelities to break the classical bound imposed by Bell’s inequality. While low error rates for state preparation, control, and measurement have been independently demonstrated, a simultaneous demonstration remained challenging. We employ advanced protocols like heralded initialization and calibration via gate set tomography (GST), to push fidelities of the full 2-qubit gate set above 99%, including state preparation and measurement (SPAM). We demonstrate a 97.17% Bell state fidelity without correcting for readout errors and violate Bell’s inequality using direct parity readout with a Bell signal of S = 2.731. Our measurements exceed the classical limit even at 1.1 K or entanglement lifetimes of 100 μs. Violating Bell’s inequality in a silicon quantum dot qubit system is a key milestone, as it proves quantum entanglement, fundamental to achieving quantum advantage. Silicon-based spin qubits are promising candidates for a scalable quantum computer. Here the authors demonstrate the violation of Bell’s inequality in gate-defined quantum dots in silicon, marking a significant advancement that showcases the maturity of this platform.

arXiv:2407.15778Nature CommunicationsApr 22, 202512 citations

Violation of Bell's inequality in Si

S. N. Coppersmith

Nature NanotechnologyMar 1, 20161 citation

Proposal for a Loophole-Free Bell Test with Electron Spins of Donors in Silicon

Fang-Yu Hong, Shi‐Jie Xiong, Yang Xiang +1 more

So far, all experimental tests of Bell inequalities which must be satisfied by all local realistic hidden-variable theories and are violated by quantum mechanical predictions have left at least one loophole open. We propose a feasible setup allowing for a loophole-free test of the Bell inequalities. Two electron spin qubits of donors31P in a nanoscale silicon host in different cavities 300 m apart are entangled through a bright coherent light and postselections using homodyne measurements. The electron spins are then read out randomly and independently by Alice and Bob, respectively, with unity efficiency in less than 0.7 µs by using optically induced spin to charge transduction detected by radio-frequency single electron transistor. A violation of Bell inequality larger than 37% and 18% is achievable provided that the detection accuracy is 0.99 and 0.95, respectively.So far, all experimental tests of Bell inequalities which must be satisfied by all local realistic hidden-variable theories and are violated by quantum mechanical predictions have left at least one loophole open. We propose a feasible setup allowing for a loophole-free test of the Bell inequalities. Two electron spin qubits of donors31P in a nanoscale silicon host in different cavities 300 m apart are entangled through a bright coherent light and postselections using homodyne measurements. The electron spins are then read out randomly and independently by Alice and Bob, respectively, with unity efficiency in less than 0.7 µs by using optically induced spin to charge transduction detected by radio-frequency single electron transistor. A violation of Bell inequality larger than 37% and 18% is achievable provided that the detection accuracy is 0.99 and 0.95, respectively.

Journal of Modern PhysicsJan 1, 20110 citations

Bell's inequality violation with spins in silicon

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