A system obtains a first operator that produces a superposition state of a plurality of random variables. The system performs iteration of a first operation and a second operation on an initial quantum state using a state maintaining unit to produce a final quantum state. The first operation produces a second state by performing a computation that inverts a first state with respect to a state obtained by applying a Hermitian conjugate of the first operator to a quantum state where the last bit of a bit string is 0. The second operation produces a new first state by performing a computation that inverts the second state with respect to the first state. The system measures the bit string in the final quantum state, records the number of hits that is the number of times a quantum state where all bits of the bit string are 0 is observed, and calculate an expectation value of the random variables by maximum likelihood estimation according to the number of hits.

In a quantum-computation method, quantum-computer code is received for execution on a quantum computer. The quantum computer includes a plurality of qubits associated with a corresponding plurality of particles, and the plurality of particles define a quantum state. The quantum-computer code is decomposed into a sequence of operations including a total spin-state measurement on particles corresponding to two or more of the qubits. Then the sequence of operations is applied on the plurality of particles to thereby transform the quantum state according to the quantum-computer code initially received.

A set of quantum controllers are operable to transmit quantum state data to a quantum control switch. The quantum control switch comprises vector processors that operate on the quantum state data from the set of quantum controllers. Each vector processor transmits a result of the operation to a corresponding quantum controller in the set of quantum controllers.

A quantum device includes a syndrome measurement circuit that implements an correction code using a plurality of Majorana qubit islands. The syndrome measurement circuit is adapted to effect a syndrome measurement by performing a sequence of measurement-only operations, where each one of the measurement-only operations involves at most two of the Majorana qubit islands.

A quantum device includes a syndrome measurement circuit that implements an correction code using a plurality of Majorana qubit islands. The syndrome measurement circuit is adapted to effect a syndrome measurement by performing a sequence of measurement-only operations, where each one of the measurement-only operations involves at most two of the Majorana qubit islands.

A system for transmission of quantum information for quantum error correction includes an ancilla qubit chip including a plurality of ancilla qubits, and a data qubit chip spaced apart from the ancilla qubit chip, the data qubit chip including a plurality of data qubits. The system includes an interposer coupled to the ancilla qubit chip and the data qubit chip, the interposer including a dielectric material and a plurality of superconducting structures formed in the dielectric material. The superconducting structures enable transmission of quantum information between the plurality of data qubits on the data qubit chip and the plurality of ancilla qubits on the ancilla qubit chip via virtual photons for quantum error correction.

A system for transmission of quantum information for quantum error correction includes an ancilla qubit chip including a plurality of ancilla qubits, and a data qubit chip spaced apart from the ancilla qubit chip, the data qubit chip including a plurality of data qubits. The system includes an interposer coupled to the ancilla qubit chip and the data qubit chip, the interposer including a dielectric material and a plurality of superconducting structures formed in the dielectric material. The superconducting structures enable transmission of quantum information between the plurality of data qubits on the data qubit chip and the plurality of ancilla qubits on the ancilla qubit chip via virtual photons for quantum error correction.

A method includes: performing transformation processing on input quantum states of n qubits through a parameterized quantum circuit, to output quantum states of the n qubits, an expected energy value of Hamiltonian of a target quantum system in the output quantum states of the n qubits being a summation result of expected energy values of k Pauli strings obtained by decomposing the Hamiltonian, n and k being positive integers; performing post-processing on the output quantum states of the n qubits by using a neural network, and obtaining the expected energy value of the Hamiltonian by calculating a post-processing result of the neural network; adjusting parameters of the parameterized quantum circuit and parameters of the neural network while aiming to converge the expected energy value of the Hamiltonian; and determining the expected energy value of the Hamiltonian satisfying the convergence condition as ground state energy of the target quantum system.

A method is provided. The method includes: determining an order of a crosstalk noise of a quantum computer; determining a set of calibration circuits based on the order of the crosstalk noise; preparing a respective standard basis quantum state based on each calibration circuit in the set of calibration circuits, the quantum measurement device is repeatedly run for a predetermined number of times for each standard basis quantum state to measure the standard basis quantum state and to obtain a predetermined number of measurement results ; performing a statistic process on the obtained predetermined number of measurement results corresponding to each standard basis quantum state, to obtain a set of calibration data; determining a global generator based on a hardware topological structure of the quantum computer and the set of calibration data; and constructing a calibration matrix based on the global generator, so as to correct the measurement results of the quantum computer based on the calibration matrix.

An entangled quantum cache includes a quantum store that receives a plurality of quantum states and is configured to store and order the plurality of quantum states and to provide select ones of the stored and ordered plurality of quantum states to a quantum data output at a first desired time. A fidelity system is configured to determine a fidelity of at least some of the plurality of quantum states. A classical store is coupled to the fidelity system and configured to store classical data comprising the determined fidelity information and an index that associates particular ones of classical data with particular ones of the plurality of quantum states and to supply at least some of the classical data to a classical data output at a second desired time. A processor is connected to the classical store and determines the first time based on the index.