Abstract: A quantum data center includes a quantum computer and a transceiver. The transceiver is in communication with the quantum computer and is operable to communicate with a remote user via a quantum communication network. The quantum computer (i) receives, via the transceiver, a quantum input state from the remote user, (ii) stores, in a quantum random access memory, a plurality of database states in a plurality of database qudits forming a database register, (iii) queries the quantum random access memory with the quantum input state to retrieve, from the database register, a quantum output state that is based on one or more of the plurality of database states, the quantum output state being disentangled from the quantum input state and the plurality of database states, and (iv) transmits, via the transceiver, the quantum output state to the remote user.

Abstract: A quantum source coding method includes: initializing a quantum register having a plurality of nodes: loading a unary-coded message into the quantum register; loading an address state into an address register of each message node of the quantum register; sorting the message nodes based on a data register such that the message nodes form a message-sorted sequence; and applying, for each message node at an end of the message-sorted sequence, a CNOT gate to the address state of each of the register's message nodes and output nodes. The method also includes: unsorting the message nodes; sorting the nodes based on the address register such that the nodes form a fully-sorted sequence; applying, for each pair of adjacent nodes in the fully-sorted sequence having the same address state, a CNOT gate to the data registers of each pair; and unsorting the nodes to return the fully-sorted sequence to the initial sequence.

Abstract: A fault tolerant quantum computer is implementing using hybrid acoustic-electric qubits. A control circuit includes an asymmetrically threaded superconducting quantum interference devices (ATS) that excites phonons in a mechanical resonator by driving a storage mode of the mechanical resonator and dissipates phonons from the mechanical resonator via an open transmission line coupled to the control circuit, wherein the open transmission line is configured to absorb photons from a dump mode of the control circuit. Filters are included in the control circuit to suppress cross-talk errors. Additionally, frequencies and pump mode detunings for respective multiplexed control circuits are strategically selected to reduce cross-talk errors.

Abstract: Extra edges are added to a group of edges for use in decoding syndrome measurements of a surface code implemented using hybrid acoustic-electric qubits. The extra edges include two-dimensional cross-edges and three-dimensional space-time correlated edges that identify correlated errors arising from spurious photon dissipation processes of a multiplexed control circuit that leads to cross-talk between storage modes of a set of the mechanical resonators controlled by the given multiplexed control circuit. Additionally, error probabilities used for edge weighting incorporate error probabilities due to the spurious photon dissipation processes.

Abstract: A method of simulating quantum gates includes shifting a Fock basis for the simulation such that the simulation can be performed in a smaller (e.g. truncated) Hilbert dimension space. To shift the Fock basis, non-orthonormalized basis states are first defined. The defined basis states are then orthonormalized to construct orthonormalized shifted Fock basis state. Matrix elements are determined for an operator in the orthonormalized shifted Fock basis and the operator is used to simulate the quantum gate in the shifted Fock basis.

Abstract: Extra edges are added to a group of edges for use in decoding syndrome measurements of a surface code implemented using hybrid acoustic-electric qubits. The extra edges include two-dimensional cross-edges and three-dimensional space-time correlated edges that identify correlated errors arising from spurious photon dissipation processes of a multiplexed control circuit that leads to cross-talk between storage modes of a set of the mechanical resonators controlled by the given multiplexed control circuit. Additionally, error probabilities used for edge weighting incorporate error probabilities due to the spurious photon dissipation processes.

Abstract: A fault tolerant quantum computer is implementing using hybrid acoustic-electric qubits. A control circuit includes an asymmetrically threaded superconducting quantum interference devices (ATS) that excites phonons in a mechanical resonator by driving a storage mode of the mechanical resonator and dissipates phonons from the mechanical resonator via an open transmission line coupled to the control circuit, wherein the open transmission line is configured to absorb photons from a dump mode of the control circuit. Filters are included in the control circuit to suppress cross-talk errors. Additionally, frequencies and pump mode detunings for respective multiplexed control circuits are strategically selected to reduce cross-talk errors.

Abstract: A method of simulating quantum gates includes shifting a Fock basis for the simulation such that the simulation can be performed in a smaller (e.g. truncated) Hilbert dimension space. To shift the Fock basis, non-orthonormalized basis states are first defined. The defined basis states are then orthonormalized to construct orthonormalized shifted Fock basis state. Matrix elements are determined for an operator in the orthonormalized shifted Fock basis and the operator is used to simulate the quantum gate in the shifted Fock basis.

Abstract: A fault tolerant quantum computer is implemented using hybrid acoustic-electric qubits. A control circuit includes an asymmetrically threaded superconducting quantum interference devices (ATS) that excites excite phonons in a mechanical resonator by driving a storage mode of the mechanical resonator and dissipates phonons from the mechanical resonator via an open transmission line coupled to the control circuit, wherein the open transmission line is configured to absorb photons from a dump mode of the control circuit.

Abstract: Techniques for implementing a QRAM by routing quantum information through multiple modes of a bosonic system are described. According to some aspects, a single bosonic system may be configured to maintain quantum information in a large number of independent modes at the same time. Suitable operations upon these modes may allow a quantum address value to be routed to modes associated with respective bits such that the only modes altered by the operations are those associated with the addresses being accessed. These modes may be operated upon based on the stored values then extracted to obtain the desired correlated superposition of the stored bit values in the addresses. The bits stored at the address locations may be classical bits, or may be qubits.

Abstract: A fault tolerant quantum computer is implemented using hybrid acoustic-electric qubits. A control circuit includes an asymmetrically threaded superconducting quantum interference devices (ATS) that excites excite phonons in a mechanical resonator by driving a storage mode of the mechanical resonator and dissipates phonons from the mechanical resonator via an open transmission line coupled to the control circuit, wherein the open transmission line is configured to absorb photons from a dump mode of the control circuit.