Estimating molecular thermal averages with the quantum equation of motion and informationally complete measurements

• URL: http://arxiv.org/abs/2406.04475v1
• Date: Thu, 6 Jun 2024 20:02:24 GMT
• Title: Estimating molecular thermal averages with the quantum equation of motion and informationally complete measurements
• Authors: Daniele Morrone, N. Walter Talarico, Marco Cattaneo, Matteo A. C. Rossi,
• Abstract summary: We use the Variational Quantum Eigensolver (VQE) to compute thermal averages of quantum systems. A drawback of qEOM is that it requires measuring the expectation values of a large number of observables on the ground state of the system. In this work we focus on measurements through informationally complete positive operator-valued measures (IC-POVMs) to achieve a reduction in the measurements overheads.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: By leveraging the Variational Quantum Eigensolver (VQE), the ``quantum equation of motion" (qEOM) method established itself as a promising tool for quantum chemistry on near term quantum computers, and has been used extensively to estimate molecular excited states. Here, we explore a novel application of this method, employing it to compute thermal averages of quantum systems, specifically molecules like ethylene and butadiene. A drawback of qEOM is that it requires measuring the expectation values of a large number of observables on the ground state of the system, and the number of necessary measurements can become a bottleneck of the method. In this work we focus on measurements through informationally complete positive operator-valued measures (IC-POVMs) to achieve a reduction in the measurements overheads. We show with numerical simulations that the qEOM combined with IC-POVM measurements ensures a satisfactory accuracy in the reconstruction of the thermal state with a reasonable number of shots.

Related papers

• Effect of the readout efficiency of quantum measurement on the system entanglement [44.99833362998488]
  We quantify the entanglement for a particle on a 1d quantum random walk under inefficient monitoring. We find that the system's maximal mean entanglement at the measurement-induced quantum-to-classical crossover is in different ways by the measurement strength and inefficiency.
  arXiv  Detail & Related papers  (2024-02-29T18:10:05Z)
• Adaptive measurement strategy for quantum subspace methods [0.0]
  We propose an adaptive measurement optimization method that is useful for the quantum subspace methods. The proposed method first determines the measurement protocol for classically simulatable states, and then adaptively updates the protocol of quantum subspace expansion. As a numerical demonstration, we have shown for excited-state simulation of molecules that we are able to reduce the number of measurements by an order of magnitude.
  arXiv  Detail & Related papers  (2023-11-14T04:00:59Z)
• Enhanced Entanglement in the Measurement-Altered Quantum Ising Chain [46.99825956909532]
  Local quantum measurements do not simply disentangle degrees of freedom, but may actually strengthen the entanglement in the system. This paper explores how a finite density of local measurement modifies a given state's entanglement structure.
  arXiv  Detail & Related papers  (2023-10-04T09:51:00Z)
• Quantum Neural Estimation of Entropies [20.12693323453867]
  entropy measures quantify the amount of information and correlation present in a quantum system. We propose a variational quantum algorithm for estimating the von Neumann and R'enyi entropies, as well as the measured relative entropy and measured R'enyi relative entropy.
  arXiv  Detail & Related papers  (2023-07-03T17:30:09Z)
• Accelerated variational quantum eigensolver with joint Bell measurement [0.0]
  We present a protocol termed joint Bell measurement VQE to reduce the number of measurements and speed up the VQE algorithm. Our approach is not limited to VQE and can be utilized in various quantum algorithms whose cost functions are expectation values of many Pauli operators.
  arXiv  Detail & Related papers  (2023-07-03T06:05:28Z)
• Potential and limitations of quantum extreme learning machines [55.41644538483948]
  We present a framework to model QRCs and QELMs, showing that they can be concisely described via single effective measurements. Our analysis paves the way to a more thorough understanding of the capabilities and limitations of both QELMs and QRCs.
  arXiv  Detail & Related papers  (2022-10-03T09:32:28Z)
• Probing finite-temperature observables in quantum simulators of spin systems with short-time dynamics [62.997667081978825]
  We show how finite-temperature observables can be obtained with an algorithm motivated from the Jarzynski equality. We show that a finite temperature phase transition in the long-range transverse field Ising model can be characterized in trapped ion quantum simulators.
  arXiv  Detail & Related papers  (2022-06-03T18:00:02Z)
• Estimating the degree of non-Markovianity using variational quantum circuits [0.0]
  We propose to use a qubit as a probe to estimate the degree of non-Markovianity of the environment. We find an optimal sequence of qubit-environment interactions that yield accurate estimations.
  arXiv  Detail & Related papers  (2022-02-28T17:14:46Z)
• Quantum expectation-value estimation by computational basis sampling [0.0]
  A practical obstacle is the necessity of a large number of measurements for statistical convergence. We propose an algorithm to estimate the expectation value based on its approximate expression as a weighted sum of classically-tractable matrix elements.
  arXiv  Detail & Related papers  (2021-12-14T14:08:56Z)
• State preparation and measurement in a quantum simulation of the O(3) sigma model [65.01359242860215]
  We show that fixed points of the non-linear O(3) sigma model can be reproduced near a quantum phase transition of a spin model with just two qubits per lattice site. We apply Trotter methods to obtain results for the complexity of adiabatic ground state preparation in both the weak-coupling and quantum-critical regimes. We present and analyze a quantum algorithm based on non-unitary randomized simulation methods.
  arXiv  Detail & Related papers  (2020-06-28T23:44:12Z)
• Direct estimation of quantum coherence by collective measurements [54.97898890263183]
  We introduce a collective measurement scheme for estimating the amount of coherence in quantum states. Our scheme outperforms other estimation methods based on tomography or adaptive measurements. We show that our method is accessible with today's technology by implementing it experimentally with photons.
  arXiv  Detail & Related papers  (2020-01-06T03:50:42Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.