Abstract: This disclosure relates to a method for estimating a solution to a problem represented by a Hamiltonian on a quantum computer having a quantum state. A classical computer determines a trial state and evolves the quantum state of the quantum computer based on the trial state. The computer then determines estimates for expectation values with respect to the trial state of powers of the Hamiltonian based on measurements from the quantum computer and calculates an estimate of the solution based on the estimates for the expectation values of powers of the Hamiltonian for the trial state. The computer then repeated updates the trial state and repeats the measuring steps to iteratively improve the estimate of the solution.

Abstract: This disclosure relates to automatic determination of locations of one or more closely spaced donor atoms implanted into a semiconductor crystal lattice. A processor receives image data generated by a scanning tunnelling microscope (STM). The image data is indicative of a tunnelling current between a scanning tip and the crystal lattice at multiple image locations. The processor applies a trained machine learning model to the image data to determine a classification into one of multiple candidate configurations of the one or more donor atoms. The multiple candidate configurations relate to different locations of the one or more donor atoms in the semiconductor crystal lattice. Based on an output of the trained machine learning model, the processor determines the location of the one or more donor atoms in the semiconductor crystal lattice.

Abstract: This disclosure relates to quantum computer arrays. In particular, a quantum processor comprises an array of source lines, drain lines and gate lines intersecting each other to define processor cells. Each of the processor cells comprise a first qubit, a second qubit and an electron confinement region disposed between the first qubit and the second qubit. A control circuit controls loading and unloading of an electron into the electron confinement region. The loading of the electron into the confinement region enables exchange interaction between electrons of the first qubit and the second qubit, and the unloading of the electron out of the electron confinement region suppresses exchange interaction between the electrons of the first qubit and the second qubit.

Abstract: The present disclosure provides a quantum processor realized in a semiconductor material and method to operate the quantum processor to implement adiabatic quantum computation. The quantum processor comprises a plurality of qubit elements disposed in a two-dimensional matrix arrangement. The qubits are implemented using the nuclear or electron spin of phosphorus donor atoms. Further, the processor comprises a control structure with a plurality of control members, each arranged to control a plurality of qubits disposed along a line or a column of the matrix. The control structure is controllable to perform adiabatic quantum error corrected computation.

Abstract: The present disclosure provides a quantum processor realized in a semiconductor material and method to operate the quantum processor to implement error corrected quantum computation. The quantum processor comprises a plurality of qubit elements disposed in a two-dimensional matrix arrangement. The qubits are implemented using the nuclear or electron spin of phosphorus donor atoms. Further, the processor comprises a control structure with a plurality of control members, each arranged to control a plurality of qubits disposed along a line or a column of the matrix. The control structure is controllable to perform topological quantum error corrected computation.

Abstract: The present disclosure provides a quantum processor realised in a semiconductor material and method to operate the quantum processor to implement adiabatic quantum computation. The quantum processor comprises a plurality of qubit elements disposed in a two-dimensional matrix arrangement. The qubits are implemented using the nuclear or electron spin of phosphorus donor atoms. Further, the processor comprises a control structure with a plurality of control members, each arranged to control a plurality of qubits disposed along a line or a column of the matrix. The control structure is controllable to perform adiabatic quantum error corrected computation.

Abstract: The present disclosure provides a quantum processor realised in a semiconductor material and method to operate the quantum processor to implement error corrected quantum computation. The quantum processor comprises a plurality of qubit elements disposed in a two-dimensional matrix arrangement. The qubits are implemented using the nuclear or electron spin of phosphorus donor atoms. Further, the processor comprises a control structure with a plurality of control members, each arranged to control a plurality of qubits disposed along a line or a column of the matrix. The control structure is controllable to perform topological quantum error corrected computation.

Abstract: This invention concerns an electronic device for the control and readout of the electron or hole spin of a single dopant in silicon. The device comprises a silicon substrate in which there are one or more ohmic contact regions. An insulating region on top of the substrate. First and second barrier gates spaced apart to isolate a small region of charges to form an island of a Single Electron Transistor (SET). A third gate over-lying both the first and second barrier gates, but insulated from them, the third gate being able to generate a gate-induced charge layer (GICL) in the beneath it. A fourth gate in close proximity to a single dopant atom, the dopant atom being encapsulated in the substrate outside the region of the GICL but close enough to allow spin-dependent charge tunnelling between the dopant atom and the SET island under the control of gate potentials, mainly the fourth gate.

Abstract: This invention concerns a quantum device, suitable for quantum computing, based on dopant atoms located in a solid semiconductor or insulator substrate. In further aspects the device is scaled up. The invention also concerns methods of reading out from the devices, initializing them, using them to perform logic operations and making them.

Abstract: This invention concerns an electronic device for the control and readout of the electron or hole spin of a single dopant in silicon. The device comprises a silicon substrate in which there are one or more ohmic contact regions. An insulating region on top of the substrate. First and second barrier gates spaced apart to isolate a small region of charges to form an island of a Single Electron Transistor (SET). A third gate over-lying both the first and second barrier gates, but insulated from them, the third gate being able to generate a gate-induced charge layer (GICL) in the ESR line substrate beneath it. A fourth gate in close proximity to a single dopant donor gate atom, the dopant atom being encapsulated in the substrate outside the region of the GICL but close enough to allow spin-dependent charge tunnelling between the dopant atom and the SET island under the control of gate potentials, mainly the fourth gate.

Abstract: This invention concerns a quantum device, suitable for quantum computing, based on dopant atoms located in a solid semiconductor or insulator substrate. In further aspects the device is scaled up. The invention also concerns methods of reading out from the devices, initializing them, using them to perform logic operations and making them.

Abstract: Ionisation of one of a pair of dopant atoms in a substrate creates a double well potential, and a charge qubit is realised by the location of one or more electrons or holes within this potential. The dopant atoms may comprise phosphorous atoms, located in a silicon substrate. A solid state quantum computer may be formed using a plurality of pairs of dopant atoms, corresponding gate electrodes, and read-out devices comprising single electron transistors.

Abstract: This invention concerns quantum computers in which the qubits are closed systems, in that the particle or particles are confined within the structure. A “site” can be produced by any method of confining an electron or other quantum particle, such as a dopant atom, a quantum dot, a cooper pair box, or any combination of these. In particular the invention concerns a closed three-site quantum particle system. The state in the third site is weakly coupled by coherent tunneling to the first and second states, so that the third state is able to map out the populations of the first and second states as its energy is scanned with respect to the first and second states. In second and third aspects it concerns a readout method for a closed three-state quantum particle system.

Abstract: According to a general aspect, the use of a quantum computer for storing a database comprising a plurality of records and searching said database for a record matching a query record, especially a record identical or similar to a query record is disclosed. The database may contain biological data; genetic data; genetic patterns, such as regular expressions, sequence profiles or hidden Markov models; or other data of interest to the user. A genetic sequence; a partial genetic sequence; or other search string may be used to query the database.