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QPU information

IBM® offers access to a wide variety of quantum processing units (QPUs). All QPUs deployed by IBM are based on superconducting qubit technology, as the control and scalability of this technology pave a clear path to achieving quantum advantage with these QPUs.

Explore all public IBM QPUs by navigating to the Compute resources page on IBM Quantum® Platform. Click any QPU to open its detailed information card.

This page describes the detailed information you will find on the QPU information card.

QPU versioning

Each QPU has a version number in the form X.Y.Z (major.minor.revision). A circuit compiled for a given version number is guaranteed to run on that QPU. If the revision number changes, the circuit will continue to run. If the major or minor number changes, the circuit is not guaranteed to run, although it may do so. The conditions under which a version number may change are listed below:

Major version

The major version will increment for changes such as:

• Sample changes.
• Major changes to the control electronics.
• Moving the QPU to a new location, if significant behavior changes result.

Minor version

The minor version will increment for changes such as:

• Warmup / cool-down cycles.
• Swapping out some electronics, if the replacement appreciably affects operation.
• Changing the direction of a controlled-NOT gate.
• Dropping a gate for some duration of time due to calibration issues, and corrections cannot readily be done in software.

Revision version

The revision version number will increment for fixes that do not break the existing compiled circuit. These changes include:

• Manual calibrations to improve fidelities.
• Small electronics changes that don’t affect operation.
• QPU software updates.

QPU details

The first section of the QPU information card provides the following QPU details:

Name | Qubits | 2Q error (best) | 2Q error (layered) | CLOPS (or CLOPS_h) | Status | Region | QPU version | Processor type | Basis gates | Total pending jobs | Median 2Q error | Median SX error | Median readout error | Median T1 (relaxation time) | Median T2 (dephasing time)

Name

The unique name assigned to a specific QPU. QPUs hosted on IBM Cloud® have names that begin with ibm_*. All QPUs are given a city name, e.g., ibm_kingston. This name does not indicate where the actual QPU is hosted. They are named after IBM® locations around the world.

Qubits

The number of physical qubits in a QPU.

2Q error (best)

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

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. Find an example notebook in the Qiskit Community GitHub.

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

The QPU status; for example, Online, Paused, Offline, and so on.

Region

Location of the data center where your data and experiments will be hosted and processed.

QPU version

The version number of a QPU in the form major.minor.revision. See QPU versioning for details on how this number is assigned.

Processor type

Reflects the topology and indicates the approximate qubit count.

Basis gates

Each processor family has a native gate set. By default, the QPUs in each family only support running the gates and operations in the native gate set. Thus, every gate in the circuit must be translated (by the transpiler) to the elements of this set. Note that the non-unitary operations are not listed here; use the method in Qiskit to see all native gates and operations for a QPU. See a list of all native gates in this table.

Total pending jobs

The total number of jobs that you have submitted to this QPU.

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.

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.

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 T1 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 T2 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. T2 is reported from a Hahn echo sequence.

Calibration data

What does `error = 1` mean?

If the benchmarking of a qubit or edge does not succeed over the course of several days, whether due to poor data quality or other internal factors, the reported error value is considered stale and will be reported as 1. This is not an indication that the qubit or edge is necessarily non-working or that the error is 1; rather, the error is considered undefined and you should proceed with caution when operating that qubit or gate.

The second section, Calibration data, provides qubit, connectivity, and gate data. You can choose to visualize the information as a map, graph, or table.

You can customize the data that is shown in each view, using the drop-down menus. For example, in the map view, you can choose the data you want to see for qubits and connections. The colored bars associated with the diagram or graph indicate the range that is shown, with the average value marked. The color maximum and minimum change depending on the QPU.

To download calibration data as a CSV file, click the download icon in the upper right corner of the Calibration data section.

In addition to the information provided in the Details section of the card, the Calibration data section also includes the following:

Topology diagram or coupling map | Readout assignment error | Prob meas0 prep1 | Prob meas1 prep0 | Readout length (ns) | ID error / √x (sx) error / Pauli-X error / RX error | Single-qubit gate length (ns)| Z-axis rotation (RZ) error | Operational | Gate length (ns) | 2Q error | RZZ error

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.

Readout assignment 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 $|0\rangle$ 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 $|1\rangle$ 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 (ns)

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.

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.

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.

Operational

Indicates whether the qubit can be utilized in circuits.

Gate length (ns)

Duration of the two-qubit gate operation.

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

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

RZZ error (Heron)

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

Two-qubit gate error (layered)

The third section 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.

View your resources

To find your available QPUs, open the Compute resources page (make sure you are signed in). Note that your selected region might impact the QPUs listed. Click a QPU to view its details.

You can also view your available QPUs by using the backends API. For example, the following code will return all of the backends that the specified instance (my_instance) can access:

   QiskitRuntimeService(instance="my_instance_CRN")
   service.backends()

Table of native gates and operations

Operation category	Name
Single-qubit gates	RZ, SX, X, ID, delay
Two-qubit gates	CZ, ECR
Fractional gates	RX (single-qubit), RZZ (two-qubit)
Non-unitary instructions	measure, reset
Control flow	if_else (classical feedforward)