Device and method for solving computational problems using a quantum system

An apparatus for computing solutions to computational problems, comprising:

• a quantum system comprising a plurality of qubits;
• a cooling unit adapted for cooling the quantum system towards a ground state of the quantum system;
• a programmable quantum annealing unit adapted for evolving, by quantum annealing, an initial Hamiltonian of the quantum system into a final Hamiltonian of the quantum system, wherein the final Hamiltonian is a sum of a problem Hamiltonian and a short-range Hamiltonian, wherein the problem Hamiltonian is a single-body Hamiltonian comprising a plurality of adjustable parameters, wherein the short-range Hamiltonian is a Hamiltonian representing interactions of a plurality of qubits, wherein no interactions in the short-range Hamiltonian occur between qubits which are distanced from each other by a distance greater than an interaction cut-off distance, wherein the interaction cut-off distance is smaller than a maximal qubit distance between the qubits;
• a measurement device adapted for measuring at least a portion of the plurality of qubits;
• and
• a classical computing system connected to the programmable quantum annealing unit and to the measurement device, wherein the classical computing system is configured for:
• receiving, as an input, a computational problem;
• encoding the computational problem into the problem Hamiltonian, wherein the encoding comprises determining, from the computational problem, a problem-encoding configuration for the plurality of adjustable parameters of the problem Hamiltonian;
• and
• communicating the problem-encoding configuration to the quantum annealing unit;
• wherein the programmable quantum annealing unit is configured for:
• receiving the problem-encoding configuration from the classical computing system;
• and
• evolving, by quantum annealing, the initial Hamiltonian into the final Hamiltonian, wherein the plurality of adjustable parameters of the problem Hamiltonian are in the problem-encoding configuration;
• and
• wherein the classical computing system is further configured for
• receiving a read-out of the quantum system from the measurement device;
• and
• determining a solution to the computational problem from the read-out.

A programmable quantum annealing device for computing solutions to computational problems, comprising:

• a quantum system comprising a plurality of superconducting qubits arranged according to a two-dimensional lattice;
• a magnetic flux bias assembly comprising a plurality of magnetic flux bias units configured for generating a plurality of adjustable magnetic fluxes, wherein each adjustable magnetic flux acts on a single superconducting qubit in the plurality of superconducting qubits;
• a coupling unit comprising at least one superconducting quantum interference device configured for coupling the plurality of superconducting qubits according to a plaquette Hamiltonian;
• and
• a controller connected to the magnetic flux bias unit and to the coupling unit, configured for:
• receiving a problem-encoding configuration for a plurality of adjustable parameters of a problem Hamiltonian of the quantum system, wherein the problem Hamiltonian is a single-body Hamiltonian, and wherein the problem-encoding configuration encodes a computational problem;
• and
• controlling the magnetic flux bias assembly and the coupling unit to evolve an initial Hamiltonian of the quantum system into a final Hamiltonian of the quantum system by quantum annealing, wherein the final Hamiltonian is the sum of the plaquette Hamiltonian and the problem Hamiltonian, wherein the plurality of adjustable parameters of the problem Hamiltonian are in the problem-encoding configuration.