title: Bell's inequality violation with spins in silicon.
abstract: Bell's theorem proves the existence of entangled quantum states with no classical counterpart. An experimental violation of Bell's inequality demands simultaneously high fidelities in the preparation, manipulation and measurement of multipartite quantum entangled states, and provides a single-number benchmark for the performance of devices that use such states for quantum computing. We demonstrate a Bell/ Clauser-Horne-Shimony-Holt inequality violation with Bell signals up to 2.70(9), using the electron and the nuclear spins of a single phosphorus atom embedded in a silicon nanoelectronic device. Two-qubit state tomography reveals that our prepared states match the target maximally entangled Bell states with >96% fidelity. These experiments demonstrate complete control of the two-qubit Hilbert space of a phosphorus atom and highlight the important function of the nuclear qubit to expand the computational basis and maximize the readout fidelity.
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Juan P
authors.identifier: http://orcid.org/0000-0002-0425-4345
authors.initials: JP
authors.lastname: Dehollain
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Simmons
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Juha T
authors.initials: JT
authors.lastname: Muhonen
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Rachpon
authors.initials: R
authors.lastname: Kalra
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Arne
authors.initials: A
authors.lastname: Laucht
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Fay
authors.initials: F
authors.lastname: Hudson
authors.affiliation: School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, 223-8522, Japan.
authors.forename: Kohei M
authors.initials: KM
authors.lastname: Itoh
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: David N
authors.initials: DN
authors.lastname: Jamieson
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: McCallum
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Dzurak
authors.affiliation: Centre for Quantum Computation and Communication Technology, UNSW Australia, Sydney, New South Wales 2052, Australia.|School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia.
authors.forename: Andrea
authors.identifier: http://orcid.org/0000-0001-7445-699X
authors.initials: A
authors.lastname: Morello