Readout Error Mitigation with FiQCI EMS

Readout Error Mitigation with FiQCI EMS#

What is Readout Error Mitigation?#

Readout errors occur when quantum measurements incorrectly identify the state of a qubit. For example, a qubit prepared in state |0⟩ might be measured as |1⟩, and vice versa. These errors are typically characterized by:

  • P(0|0): Probability of correctly measuring 0 when qubit is in state |0⟩

  • P(1|0): Probability of incorrectly measuring 1 when qubit is in state |0⟩

  • P(0|1): Probability of incorrectly measuring 0 when qubit is in state |1⟩

  • P(1|1): Probability of correctly measuring 1 when qubit is in state |1⟩

The M3 (Matrix-free Measurement Mitigation) Method#

M3 is a readout error mitigation technique that:

  1. Calibrates by running circuits that prepare known computational basis states

  2. Characterizes the confusion matrix describing measurement errors

  3. Corrects measured distributions by inverting the error model

Unlike traditional methods that explicitly compute and invert large matrices, M3 uses tensor network methods to efficiently handle multi-qubit systems, making it scalable to larger quantum computers.

Key advantages of M3:

  • Scales efficiently to many qubits

  • Handles correlated and uncorrelated readout errors

  • Provides quasi-probability distributions (can have negative values)

  • Can convert to nearest valid probability distribution

Advanced: Direct M3IQM Control#

For fine-grained control over the mitigation process, you can use the M3IQM class directly. This allows you to:

  • Choose calibration strategies ("balanced", "independent", "marginal")

  • Inspect per-qubit calibration matrices

  • Apply correction manually and access quasi-probability distributions

  • Calculate expectation values and standard deviations from quasi-distributions

See the Advanced Readout Error Mitigation example for a full walkthrough.

Examples#

References:#