Noise Profiler
This page uses the terminology and concepts discussed in the Quantum Architecture Basics section.
Introduction
Figure 6. Flow diagram of TopQAD’s Noise Profiler service, which runs its Noise Profiler tool to determine the logical performance of fault-tolerant algorithms using given hardware specifications. Code distance is one factor determining the physical microarchitecture requirements; thus, the Noise Profiler can be used to study the requirements of future quantum architectures.
The Noise Profiler automates the process of profiling logical performance of FTQC protocols, such as quantum memory or teleportation, based on hardware noise characteristics. This enables you to quickly run simulation experiments to guide the design and evaluation of your quantum computer towards FTQC. The Noise Profiler includes methods for estimating performance at scales and for parameter values beyond those directly accessible via simulation.
For example, the Noise Profiler can help answer the following questions:
Quantum processing unit (QPU) and controller
- What error rates will certain (e.g., baseline, target, or desired) hardware specifications create when executing different FTQC protocols?
- Which hardware specifications are most important to focus on and/or improve? How do they trade off?
- How does a given fabrication process variability affect the performance of the FTQC?
Decoder
- What error rates does a particular decoder generate when integrated with certain target hardware?
Portal Specifications
Noise Profiler Portal Access Specifications
Inputs
| Parameter | Description | |
|---|---|---|
| Code | Specifier | The QECC to use. Currently, the “Rotated surface code” is supported. |
| Protocol | Specifier | The FTQC protocol to profile with the given hardware noise parameters. Subsequent protocol parameters will update based on the selected specifier. Currently, the “Fault-tolerant quantum memory ” protocol is supported. |
| Number of rounds | The number of stabilization cycles in the protocol. This option is available for the “Fault-tolerant quantum memory ” protocol. | |
| Decoder | Specifier | The decoder to use. Currently, “Minimum-weight perfect matching” is supported. |
| Physical qubit and gate characterization | Qubit measurement time | The time taken to measure a qubit. |
| Qubit preparation time | The time taken to prepare a qubit in a zero or one state at the start of a protocol. | |
| Qubit reset time | The time taken to reset a qubit to the zero state mid-protocol. | |
| Single-qubit gate time | The time taken to implement single-qubit gates (e.g., the Hadamard gate) | |
| Two-qubit gate time | The time taken to implement two-qubit gates (e.g., the controlled-NOT, or CNOT, gate). | |
| T1 relaxation time | The relaxation time for a qubit. | |
| T2 dephasing time | The dephasing time for a qubit. Currently, TopQAD requires this value to be equal to the T1 relaxation time. | |
| Measurement fidelity | The fidelity of measuring a physical qubit, that is, the average probability of an output of 0 when measuring the zero state and an output of 1 when measuring the one state. | |
| Preparation fidelity | The fidelity of preparing a qubit at the start of the protocol, that is, the average probability of preparing the zero state when trying to prepare the zero state, and preparing the one state when trying to prepare the one state. | |
| Reset fidelity | The fidelity of resetting a qubit mid-protocol, that is, the average probability of correctly resetting to the zero state regardless of the outcome of the preceding measurement. | |
| Single-qubit gate fidelity | The fidelity of implementing single-qubit gates (e.g., the Hadamard gate). | |
| Two-qubit gate fidelity | The fidelity of implementing two-qubit gates (e.g., the CNOT gate). |
Outputs
| Parameter | Description | |
|---|---|---|
| General | Elapsed time | The time taken to run the noise profiling. |
| Stabilization time | The time taken to perform one cycle of stabilizer measurements (i.e., parity checks on QEC codes). | |
| Functional form | The fitting function for the logical error rate as a function of distance. | |
| Fitting parameters | For the memory protocol, the logical error rate as a function of the distance. The logical error rate is fit, and the fitting parameters are returned. The fitting parameter determines the rate at which the logical error rate decreases with distance, while the parameter determines the rate at low distances. | |
| Logical error rate plot | A graph displaying the regression function derived from the FTQC emulations for the expected logical error rate produced by different code distances. |
SDK Specifications
Noise Profiler SDK Access Specifications
The release of an SDK is upcoming; stay tuned.