Abstract: A quantum optimization system and method estimate, on a classical computer and for a quantum state, an expectation value of a Hamiltonian, expressible as a linear combination of observables, based on expectation values of the observables; and transform, on the classical computer, one or both of the Hamiltonian and the quantum state to reduce the expectation value of the Hamiltonian.

Abstract: Model-free error correction in quantum processors is provided, allowing tailoring to individual devices. In various embodiments, a quantum circuit is configured according to a plurality of configuration parameters. The quantum circuit comprises an encoding circuit and a decoding circuit. Each of a plurality of training states is input to the quantum circuit. The encoding circuit is applied to each of the plurality of training states and to a plurality of input syndrome qubits to produce encoded training states. The decoding circuit is applied to each of the encoded training states to determine a plurality of outputs. A fidelity of the quantum circuit is measured for the plurality of training states based on the plurality of outputs. The fidelity is provided to a computing node. The computing node determines a plurality of optimized configuration parameters. The optimized configuration parameters maximize the accuracy of the quantum circuit for the plurality of training states.

Abstract: A hybrid quantum-classical (HQC) computer which includes both a classical computer component and a quantum computer component performs generative learning on continuous data distributions. The HQC computer is capable of being implemented using existing and near-term quantum computer components having relatively low circuit depth.

Abstract: A system and method include techniques for: generating, by a quantum autoencoder, based on a set of quantum states encoded in a set of qubits, a decoder circuit that acts on a subset of the set of qubits, a size of the subset being less than a size of the set; and generating a reduced-cost circuit, the reduced-cost circuit comprising: (1) a new parameterized quantum circuit acting only on the subset of the set of qubits, and (2) the decoder circuit.

Abstract: Preparation of correlated fermionic states on a quantum computer for determining a ground state of a correlated fermionic system is provided. In various embodiments, a quantum circuit is provided that comprises a linear chain of qubits and a plurality of matchgates arranged in layers. Each matchgate is configured to perform a two-qubit rotation on neighboring qubits within the linear chain. An initial state is provided for each qubit in the linear chain, The quantum circuit is applied to the initial values, thereby preparing an ansastz on the linear chain of qubits, the ansatz corresponding to a fermionic state.

Abstract: A computer-implemented method produces a representation of a pure quantum state from a classical model. The classical model has a plurality of parameters. The method includes: (A) selecting a set of outcomes from a library of outcomes of a quantum circuit, wherein the library of outcomes comprises a plurality of measurement pairs sampled from the quantum circuit, each measurement pair comprising a quantum measurement and a corresponding measurement basis; and (B) updating values of the plurality of parameters of the classical model to minimize a value of a distance measure between the classical model and the set of outcomes, thereby producing the updated classical model, wherein the updated classical model has the updated values of the plurality of parameters.

Abstract: Preparation of correlated fermionic states on a quantum computer for determining a ground state of a correlated fermionic system is provided. In various embodiments, a quantum circuit is provided that comprises a linear chain of qubits and a plurality of matchgates arranged in layers. Each matchgate is configured to perform a two-qubit rotation on neighboring qubits within the linear chain. An initial state is provided for each qubit in the linear chain, The quantum circuit is applied to the initial values, thereby preparing an ansastz on the linear chain of qubits, the ansatz corresponding to a fermionic state.

Abstract: Model-free error correction in quantum processors is provided, allowing tailoring to individual devices. In various embodiments, a quantum circuit is configured according to a plurality of configuration parameters. The quantum circuit comprises an encoding circuit and a decoding circuit. Each of a plurality of training states is input to the quantum circuit. The encoding circuit is applied to each of the plurality of training states and to a plurality of input syndrome qubits to produce encoded training states. The decoding circuit is applied to each of the encoded training states to determine a plurality of outputs. A fidelity of the quantum circuit is measured for the plurality of training states based on the plurality of outputs. The fidelity is provided to a computing node. The computing node determines a plurality of optimized configuration parameters. The optimized configuration parameters maximize the accuracy of the quantum circuit for the plurality of training states.

Abstract: A hybrid quantum classical (HQC) computer which includes both a classical computer component and a quantum computer component performs generative learning on continuous data distributions. The HQC computer is capable of being implemented using existing and near-term quantum computer components having relatively low circuit depth.

Abstract: A quantum optimization system and method estimate, on a classical computer and for a quantum state, an expectation value of a Hamiltonian, expressible as a linear combination of observables, based on expectation values of the observables; and transform, on the classical computer, one or both of the Hamiltonian and the quantum state to reduce the expectation value of the Hamiltonian.

Abstract: A system and method include techniques for: generating, by a quantum autoencoder, based on a set of quantum states encoded in a set of qubits, a decoder circuit that acts on a subset of the set of qubits, a size of the subset being less than a size of the set; and generating a reduced-cost circuit, the reduced-cost circuit comprising: (1) a new parameterized quantum circuit acting only on the subset of the set of qubits, and (2) the decoder circuit.