Abstract: A quantum information processor (QIP) may include a plurality of quantum registers, each quantum register containing at least one nuclear spin and at least one localized electronic spin. At least some of the quantum registers may be coherently coupled to each other by a dark spin chain that includes a series of optically unaddressable spins. Each quantum register may be optically addressable, so that quantum information can be initialized and read out optically from each register, and moved from one register to another through the dark spin chain, though an adiabatic sequential swap or through free-fermion state transfer. A scalable architecture for the QIP may include an array of super-plaquettes, each super-plaquette including a lattice of individually optically addressable plaquettes coupled to each other through dark spin chains, and separately controllable by confined microwave fields so as to permit parallel operations.

Abstract: A quantum ticket is defined by a unique serial number; and a set of qubits, each qubit encoding quantum information. The serial number and the set of qubits are distributed only among one or more trusted verifiers who require a tolerance fidelity Ftol in order to authenticate the token, where Ftol represents a minimum percentage of correct outcomes during authentication of the serial number and the set of qubits. The experimental fidelity Fexp for the quantum token is greater than the Ft0i set by the verifiers, so that an honest user of the quantum ticket who achieves Fexp is exponentially likely to be successfully authenticated when seeking authentication by any of the trusted verifiers. The forging fidelity Fforg for the quantum token is less than Ft0i, so that a dishonest user who achieves Fforg and attempts forgery of the quantum ticket is exponentially likely to fail to obtain authentication for his forged ticket.

Abstract: A quantum information processor (QIP) may include a plurality of quantum registers, each quantum register containing at least one nuclear spin and at least one localized electronic spin. At least some of the quantum registers may be coherently coupled to each other by a dark spin chain that includes a series of optically unaddressable spins. Each quantum register may be optically addressable, so that quantum information can be initialized and read out optically from each register, and moved from one register to another through the dark spin chain, though an adiabatic sequential swap or through free-fermion state transfer. A scalable architecture for the QIP may include an array of super-plaquettes, each super-plaquette including a lattice of individually optically addressable plaquettes coupled to each other through dark spin chains, and separately controllable by confined microwave fields so as to permit parallel operations.

Abstract: The invention provides systems and methods enabling high fidelity quantum communication over long communication channels even in the presence of significant loss in the channels. The invention involves laser manipulation of quantum correlated atomic ensembles using linear optic components (110, 120), optical sources of low intensity pulses (10), interferers in the form of beam splitters (150), and single-photon detectors (180, 190) requiring only moderate efficiencies. The invention provides fault-tolerant entanglement generation and connection using a sequence of steps that each provide built-in entanglement purification and that are each resilient to realistic noise levels. The invention relies upon collective rather single particle excitations in atomic ensembles and results in communication efficiency scaling polynomially with the total length of the communication channel.

Abstract: Apparatus and methods for high fidelity quantum communication over long communication channels even in the presence of significant loss in the channels are disclosed. The invention employs laser manipulation of quantum correlated atomic ensembles using linear optic components, optical sources of low intensity pulses, beam splitters, and single-photon detectors requiring only moderate efficiencies. The invention provides fault-tolerant entanglement generation and connection, using a sequence of steps that each provide built-in entanglement purification and that are each resilient to the realistic noise. The invention relies upon collective excitation in atomic ensembles rather than single particle excitations in atomic ensembles so that communication efficiency scales polynomially with the total length of a communication channel.

Abstract: The invention provides systems and methods enabling high fidelity quantum communication over long communication channels even in the presence of significant loss in the channels comprising laser manipulation of quantum correlated atomic ensembles using linear optic components (110, 120), optical sources of low intensity pulses (10), beam splitters (150), single-photon detectors (180, 190) requiring only moderate efficiencies. The invention provides fault-tolerant entanglement generation, connection, using a sequence of steps that each provide built-in entanglement purification and are each resilient to the realistic noise. The invention relies upon collective rather single particle excitations in atomic ensembles and result in communication efficiency scaling polynomially with the total length of a communication channel.