# Introduction to Protocols¶

True-Q™ provides a number of diagnostic and assessment protocols for generating and characterizing gates, cycles and full circuits. These protocols are described in detail in Error Diagnostics.

To get a sense of what these different protocol methods create, here is a simple example generating circuits for single qubit Streamlined Randomized Benchmarking (SRB) experiment:

import trueq as tq
circuits = tq.make_srb(labels=[0],
n_random_cycles=[4, 32],
n_circuits=25)


In this example circuits is a single qubit CircuitCollection, a collection of circuits to be run. The CircuitCollection object is essentially an iterable object of Circuits, each of which describes a single circuit to be run on a quantum device. A circuit stores both the quantum operations to be performed in each cycle of the circuit, and the experimental or simulated results once it has been run.

There are three essential steps for every protocol:

1. Generate a circuit collection using a function such as make_srb() as above or any of the other functions in Error Diagnostics.

2. Iterate through the circuit objects and perform them experimentally, recording their Results. See Examples for a number of worked examples using the Simulator.

3. Analyze the data using the fit() method of the circuit collection.

## Inspecting Generated Circuits¶

Since a CircuitCollection is effectively a list of circuits, individual circuits can be inspected using standard list indexing:

circuits[0].draw()


Every circuit generated using a make_* protocol in True-Q™ additionally contains a Key used to store information about the generation method used. This meta data can be viewed using trueq.Circuit.key.

circuits[0].key

Key(compiled_pauli='Y', n_random_cycles=4, protocol='SRB', twirl=Twirl({(0,): 'C'}, dim=2))


The Key of each circuit is essentially a hashable frozen dictionary containing data about how the circuits were generated. This information is used internally by True-Q™ during analysis, but it is often useful for the user to be able to read them. Some of the more frequently generated keys entries are listed below:

protocol -

The characterization protocol used to generate a circuit.

cycle -

A “clock cycle” of a circuit; a set of operations that happen in parallel to a disjoint set of systems.

n_random_cycles -

The number of independent random cycles in the circuit.

measurement_basis -

An n-qubit Pauli operator describing the change-of-basis gates added prior to measurement.

twirl -

The twirling group used to generate a circuit.

compiled_pauli -

The n-qubit Pauli operator that was compiled into the circuit immediately before measurement.

n_bodies -

The number of gate bodies to reconstruct marginal probability distributions for.

seq_label -

A number to group related sequences used internally by some fitting tools.

Each circuit generated by one of the protocol generation methods will have its own key. All keys present in any CircuitCollection can be viewed using its keys() method. Here we can view all keys present in the SRB circuit collection created above:

circuits.keys()

True-Q formatting will not be loaded without trusting this notebook or rerunning the affected cells. Notebooks can be marked as trusted by clicking "File -> Trust Notebook".
 KeySet List of all the keys in the KeySet protocol The characterization protocol used to generate a circuit. twirl The twirling group used to generate a circuit. n_random_cycles The number of independent random cycles in the circuit. compiled_pauli The n-qubit Pauli operator that was compiled into the circuit immediately before measurement. Key Key: compiled_pauli: I n_random_cycles: 4 protocol: SRB twirl: Cliffords on [0] SRB Cliffords on [0] 4 I Key Key: compiled_pauli: X n_random_cycles: 4 protocol: SRB twirl: Cliffords on [0] SRB Cliffords on [0] 4 X Key Key: compiled_pauli: Y n_random_cycles: 4 protocol: SRB twirl: Cliffords on [0] SRB Cliffords on [0] 4 Y Key Key: compiled_pauli: Z n_random_cycles: 4 protocol: SRB twirl: Cliffords on [0] SRB Cliffords on [0] 4 Z Key Key: compiled_pauli: I n_random_cycles: 32 protocol: SRB twirl: Cliffords on [0] SRB Cliffords on [0] 32 I Key Key: compiled_pauli: X n_random_cycles: 32 protocol: SRB twirl: Cliffords on [0] SRB Cliffords on [0] 32 X Key Key: compiled_pauli: Y n_random_cycles: 32 protocol: SRB twirl: Cliffords on [0] SRB Cliffords on [0] 32 Y Key Key: compiled_pauli: Z n_random_cycles: 32 protocol: SRB twirl: Cliffords on [0] SRB Cliffords on [0] 32 Z