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Overview

Quantum processing units (QPUs) hold the promise of revolutionizing various fields by harnessing the principles of quantum mechanics to solve problems more efficiently than classical computers. However, quantum computers are prone to noisy operations, rendering the computation results meaningless for long computation. Quantum error mitigation (EM) reduces the effect of noise on quantum algorithms by trading off QPU time for accuracy, thus extending the circuit volume available by a few orders of magnitudes, and bringing quantum advantage closer. The main advantage of EM over quantum error correction (EC) is that the former requires zero (or a few) additional qubits, making it a primary tool for the NISQ and MegaQuOp eras. Even when EC is commonly utilized, as long as high-quality qubits are invaluable, EM is would continue to boost available circuit volumes and play an important role in quantum computation.

Having outlined our vision for the future, Qedma now introduces QESEM (Quantum Error Suppression and Error Mitigation), our state-of-the-art suite for quantum algorithm developers. With QESEM, users can run their quantum circuits on noisy QPUs to obtain highly accurate error-free results with highly efficient QPU-time overheads, close to fundamental bounds. To achieve this, QESEM leverages a suite of propriety methods developed by Qedma, for the characterization and reduction of errors. Error reduction techniques include gate optimization, noise-aware transpilation, error suppression (ES), and unbiased EM. With this combination of these characterization-based methods, users can achieve reliable, error-free results for generic large-volume quantum circuits, unlocking applications that cannot be accomplished otherwise.

Description

You can use the QESEM function by Qedma to easily estimate and execute your circuits with error suppression and mitigation, achieving larger circuit volumes and higher accuracies. To use QESEM, you provide a quantum circuit, a set of observables to measure, a target statistical accuracy for each observable, and a chosen QPU. Before you run the circuit to the target accuracy, you can estimate the required QPU time based on an analytical calculation that does not require circuit execution. Once you are satisfied with the QPU time estimation, you can execute the circuit with QESEM.

When you execute a circuit, QESEM runs a device characterization protocol tailored to your circuit, yielding a reliable noise model for the errors occurring in the circuit. Based on the characterization, QESEM first implements noise-aware transpilation to map the input circuit onto a set of physical qubits and gates, which minimizes the noise affecting the target observable. These include the natively available gates (CX/CZ on IBM® devices), as well as additional gates optimized by QESEM, forming QESEM’s extended gate set. QESEM then runs a set of characterization-based ES and EM circuits on the QPU and collects their measurement outcomes. These are then classically post-processed to provide an unbiased expectation value and an error bar for each observable, corresponding to the requested accuracy.

Qedma QESEM overview

Core Advantages

QESEM has been demonstrated to provide high-accuracy results for a variety of quantum applications and on the largest circuit volumes achievable today. QESEM offers the following user-facing features, demonstrated in the benchmarks section below:

  • Guaranteed accuracy: QESEM outputs unbiased estimations for expectation values of observables. Its EM method is equipped with theoretical guarantees, which - together with Qedma’s cutting-edge characterization - ensure the mitigation converges to the noiseless circuit output up to the user-specified accuracy. In contrast to many heuristic EM methods that are prone to systematic errors or biases, QESEM’s guaranteed accuracy is essential for ensuring reliable results in generic quantum circuits and observables.
  • Scalability to large QPUs: QESEM’s QPU time depends on circuit volumes, but is otherwise independent of the number of qubits. Qedma has demonstrated QESEM on the largest quantum devices available today, including the IBM Quantum 127-qubit Eagle and 133-qubit Heron devices.
  • Application-agnostic: QESEM has been demonstrated on a variety of applications, including Hamiltonian simulation, VQE, QAOA, and amplitude estimation. Users can input any quantum circuit and observable to be measured, and obtain accurate error-free results. The only limitations are dictated by the hardware specifications and allocated QPU time, which determine the accessible circuit volumes and output accuracies. In contrast, many error reduction solutions are application-specific or involve uncontrolled heuristics, rendering them inapplicable for generic quantum circuits and applications.
  • Fractional-angle gates: QESEM enables efficient mitigation with fractional-angle gates on Heron devices, allowing more efficient compilation and unlocking circuit volumes up to 2× larger than with default CZ compilation.
  • Multibase observables: QESEM supports input observables composed of many non-commuting Pauli strings, such as generic Hamiltonians. The choice of measurement bases and the optimization of QPU resource allocation (shots and circuits) is then performed automatically by QESEM to minimize the required QPU time for the requested accuracy. This optimization, which takes into account hardware fidelities and execution rates, enables you to run deeper circuits and obtain higher accuracies.

Next Steps