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T1 (Relaxation time)

The $T_1$ time represents the average duration a qubit remains in its excited state $|1\rangle$ before decaying to its ground state $|0\rangle$ due to energy relaxation. This parameter is used to characterize the qubit's energy relaxation behavior, and is expressed in units of seconds (s).

T2 (Dephasing time)

The $T_2$ time denotes the timescale over which a qubit maintains phase coherence of a superposition between the $|0\rangle$ and $|1\rangle$ states. It accounts for both energy relaxation and pure dephasing processes, providing insight into the qubit's coherence properties.

frequency

This parameter specifies the resonant frequency of the qubit, indicating the energy difference between the $|0\rangle$ and $|1\rangle$ states, expressed in hertz (Hz).

anharmonicity

Anharmonicity is the difference in energy between the first and second excited states of the qubit, also expressed in hertz (Hz).

readout_error

The readout error quantifies the average probability of incorrectly measuring a qubit's state. It is commonly calculated as the mean of prob_meas0_prep1 and prob_meas1_prep0, providing a single metric for measurement fidelity.

prob_meas0_prep1

This parameter indicates the probability of measuring a qubit in the 0 state when it was intended to be prepared in the $|1\rangle$ state, denoted as $P(0 | 1)$. It reflects errors in state preparation and measurement (SPAM), particularly measurement errors in superconducting qubits.

prob_meas1_prep0

Similarly, this parameter represents the probability of measuring a qubit in the 1 state when it was intended to be prepared in the $|0\rangle$ state, denoted as $P(1 | 0)$. Like prob_meas0_prep1, it reflects SPAM errors, with measurement errors being the predominant contributor in superconducting qubits.

readout_length

The readout_length specifies the duration of the readout operation for a qubit. It measures the time from the initiation of the measurement pulse to the completion of signal digitization, after which the system is ready for the next operation. Understanding this parameter is crucial for optimizing circuit execution, especially when incorporating mid-circuit measurements.

2Q error (Heron: CZ, Eagle: ECR)

The two-qubit error per edge from the same batch of measurements used to calculate the 2Q median and 2Q best errors.

ID error / √x (sx) error / Pauli-X error / RX error

Error in the finite-duration discrete one-qubit gates, measured from randomized benchmarking. The randomized benchmarking sequence includes SX, ID, and X gates, and it is assumed their errors are the same. The ID gate is a delay of duration equal to the duration of the √X and X gates. The RX gate is also the same duration as the √X and X gates with variable amplitude, and so it is reported as having the same error as these gates.

2Q error (layered)

Average error per layered gate (EPLG) in a chain of 100 qubits. Average EPLG measures the average gate error in a layered chain of $N$ qubits ($N$=100 here). It is derived from a similar quantity known as the layer fidelity (LF) where EPLG$_{100}$ = 4/5(1-LF$^{\frac{1}{99}}$) and layer fidelity is the process fidelity of the layered chain of $N$ qubits. For details, see the paper Benchmarking quantum processor performance at scale. Note that in the paper EPLG is defined for process error, but for consistency with the individually reported gate errors here it is quoted for average gate error, thus the factor of 4/5.

On IBM Quantum Platform, the detailed information card for each QPU has a section called Two-qubit gate error (layered), which provides the expanded view of the lowest two-qubit gate error (layered) measured as a function of the number of qubits in the chain. The final value, at chain length 100, is the value presented in the Details section. In practice, six 100-qubit chains (pre-selected based on expected optimal performance) are measured, and the value reported for number of qubits N is the lowest error found in a subset length N chain searching over the six 100-qubit chains.

Median 2Q error (Heron: CZ, Eagle: ECR)

Average gate fidelity of the two-qubit operation from randomized benchmarking. Measured in "isolation": batches with a minimum separation of two qubits between edges. This randomized benchmarking uses alternating layers of single-qubit Cliffords and two-qubit gates, and thus the final 2Q error value includes the error of the layer of single-qubit Cliffords. Find an example notebook in the Qiskit Community GitHub. Find per-edge data in the calibration data section of the QPU information card.

2Q error (best)

The lowest two-qubit error on any edge of the device from the same batch of measurements used to calculate the median (see Median 2Q error).

Median SX error

Average gate fidelity of the √X (SX) gate from randomized benchmarking, measured simultaneously on all qubits. The randomized benchmarking sequence includes SX, ID, and X gates, and it is assumed their errors are the same.

RZZ error (Heron)

Error in the RZZ gate averaged over the RZZ angles using a variant of randomized benchmarking for arbitrary unitaries.

Median readout error

Fidelity of the readout operation. Readout error is measured by preparing the qubit in the 0 (1) state and measuring the probability of an output in the 1 (0) state. The reported value is the average of these two errors. The median is taken over all qubits.

Median T1 (relaxation time)

The $T_1$ time represents the average duration a qubit remains in its excited state $|1\rangle$ before decaying to its ground state $|0\rangle$ due to energy relaxation. This parameter is used to characterize the qubit's energy relaxation behavior, and is expressed in units of seconds (s).

Median T2 (dephasing time)

The $T_2$ time denotes the timescale over which a qubit maintains phase coherence of a superposition between the $|0\rangle$ and $|1\rangle$ states. It accounts for both energy relaxation and pure dephasing processes, providing insight into the qubit's coherence properties. $T_2$ is reported from a Hahn echo sequence.

Single-qubit gate length (ns)

Duration of a single-qubit gate operation.

Z-axis rotation (RZ) error

Error in the virtual RZ gate. Reported as all 0 since these are performed in software.

Gate length (ns)

Duration of the two-qubit gate operation.

CLOPS (or CLOPS_h)

Circuit layer operations per second, is a measure of how many layers of a 100x100 circuit (hardware-aware circuit) a QPU (quantum processing unit) can execute per unit of time. Find the CLOPS code in the Qiskit Community GitHub.

Status

With BackendStatus, you can find the QPU status (for example, Active, Paused, Offline) as well as the number of pending jobs.

Topology diagram or coupling map

A diagram that indicates the pairs of qubits that support two-qubit gate operations between them. This is also called the coupling map or connectivity. Qubits are represented as circles and the supported two-qubit gate operations are displayed as lines connecting the qubits.