Abstract: A method is provided for computational approximation of an expectation value in a finite dimensional quantum system described in a basis of linearly and algebraically independent basis operators, a set of monomials composed of the basis operators forming a basis of an operator space of linear operators associated with a Hilbert space of the quantum system. The method includes receiving a representation of an initial state operator ?ini of the quantum system, a sequence =L? . . . ?2?1 of L quantum operations i represented in terms of the monomials and an operator O represented as a linear combination of the monomials.

Abstract: In one aspect, there is provided a noise mitigation method for an execution of a quantum circuit by a quantum processor. In another aspect, there is provided a computing system comprising a quantum processor and a classical computer, the computing system being configured to carry out the method. In another aspect, there is a computer program product including instructions which, when the program is carried out by a computer system comprising a classical computer and a quantum processor, cause the computer system to carry out the method. In another aspect, there is provided a computer program product including instructions which, when the program is carried out by a classical computer, cause the classical computer to carry out the tensor network contractions according to the method.

Abstract: In one aspect, there is provided a noise mitigation method for an execution of a quantum circuit by a quantum processor. In another aspect, there is provided a computing system comprising a quantum processor and a classical computer, the computing system being configured to carry out the method. In another aspect, there is a computer program product including instructions which, when the program is carried out by a computer system comprising a classical computer and a quantum processor, cause the computer system to carry out the method. In another aspect, there is provided a computer program product including instructions which, when the program is carried out by a classical computer, cause the classical computer to carry out the tensor network contractions according to the method.

Abstract: The invention is related to a method for estimating a value of an observable quantity of a quantum system, said observable quantity being associated with a Hermitian operator O, the method comprising: Providing measurement means, said measurement means being operative to implement an informationally complete quantum measurement on said quantum system, Reconstructing M effects ?m constituting an informationally complete Positive Operator Valued Measure corresponding to said informationally complete quantum measurement by using Quantum Detector Tomography applied to said measurement means, the effect ?m being associated with a measurement outcome m, Implementing said informationally complete quantum measurement on S copies of said quantum system by using said measurement means to thereby obtain a set of measurement data (I) with m(s) being a measurement outcome for the s-th copy, Estimating said value of said observable quantity via an estimator (II), wherein ?m are the expansion coefficients of the Hermitian o

Abstract: In one aspect, there is provided a noise mitigation method for an execution of a quantum circuit by a quantum processor. In another aspect, there is provided a computing system comprising a quantum processor and a classical computer, the computing system being configured to carry out the method. In another aspect, there is a computer program product including instructions which, when the program is carried out by a computer system comprising a classical computer and a quantum processor, cause the computer system to carry out the method. In another aspect, there is provided a computer program product including instructions which, when the program is carried out by a classical computer, cause the classical computer to carry out the tensor network contractions according to the method.

Abstract: The present invention relates to a method for estimating a value of an observable quantity of a state of a quantum many-body system, and to an apparatus for carrying out said method.