Programming Quantum Computers with Qiskit and Qiskit...• Define quantum registers • Build quantum circuits • Compile circuits to run on desired backend • Submit jobs (in Qobj

Programming Quantum Computers with Qiskit

Doug McClureIBM Research

WiSQCEJanuary 2020

Overview

arxiv.org/pdf/1905.02666.pdf

• Cloud-based quantum computers

• Composing quantum circuits

• The elements of Qiskit

• IQX platform tour

• What’s next

• Demo

IBM Q Experience

Launched May 4, 2016

Free, cloud-based GUI and programmatic access to small quantum devices and simulators

Detailed user guide with example algorithms

> 160,000 users

> 20 million experiments

> 200 scientific papers

© 2017 IBM Corporation4

Quantum computing through the cloud

Classical computer API server

Control computer

Control instruments

Quantum computer


Quantum computing through the cloud

Writing quantum circuits: the “quantum score”


• “Textbook” way of showing quantum circuits

• Conducive to user-friendly drag-and-drop interface

• Useful for beginners studying simple circuits

• Becomes unmanageable for large/complex circuits

Writing quantum circuits: OpenQASM


• Text-based circuit representation

• Equivalent to quantum score▪ The OpenQASM at right represents the quantum score on

the previous slide

• Good for sending basic commands to a quantum computer

• Not useful for writing circuits manually, but amenable to programmatic generation

Full specification: arxiv.org/pdf/1707.03429.pdf

Writing quantum circuits: OpenPulse


• An even lower level than OpenQASM: direct control over theanalog pulses being sent to control and measure the qubits

• Programmatic generationis critical for building eventhe simplest circuits

Quantum programming desires

• Build and run circuits

• Study and mitigate errors

• Simulate device behavior

• Solve real-world problems

The elements of Qiskit





Terra

Aqua

Aer

Ignis

Open Source (Apache 2.0)

Written in Python 3

Modular and extendible

qiskit.org


The elements of Qiskit in action

Aqua

• Import problem

parameters from

domain-specific

software

• Execute suitable

algorithm in Terra

• Analyze results

and iterate as

appropriate to

solve problem

Terra

• Define quantum

registers

• Build quantum

circuits

• Compile circuits to

run on desired

backend

• Submit jobs (in

Qobj format) to

backends

• Retrieve results

Tutorials(Jupyter notebook-based)

• Run algorithms

• Visualize results

AerQASM simulator,

statevector simulator,

unitary simulator

Real backend A

computer, instruments,

wiring, quantum chip

AP

I S

erv

er

Real backend B

computer, instruments,

wiring, quantum chip

Simulator A

HPC cluster

Qobj

quantum

object

Results

(real or sim)

Results

(simulated)Instructions

Instructions

Results

Results

Ignis• Analysis and mitigation of noise and errors


Aqua

Aer

Ignis

Qiskit Terra





Terra


Qiskit Terra

▪Define → build → compile → run → retrieveCompile and run Get resultsBuild quantum circuits

State Counts

00000 513

00011 487

00000 00011

0.5

0.0

Pro

ba

bil

ity

Outcome

Qiskit Terra: building circuits

• QuantumCircuit(M,N) instantiates a quantum circuitacting on M quantum bits and N classical bits▪ Circuit operations are invoked as methods of this object

▪ Commonly used operations are defined in qiskit.extensions.standardo Single-qubit gates (iden, x, y, z, h, s, sdg, t, tdg, u1, u2, u3)

o Two-qubit gates (cx, cy, cz, cu1, cu2)

o Measurement, reset, and barrier (measure, reset, barrier)

• Example: prepare a Bell state▪ Make a circuit with 2 qubits and 2 bits

▪ Hadamard (h) on qubit 0

▪ CNOT (cx) from qubit 0 to qubit 1

Qiskit Terra: combining circuits

• Many ways to make complex circuits from simple ones

• Easiest is to use the + operator

• Example: measuring a Bell state in different bases

• Measurement is naturally in the Z basis

• Hadamard prior to measurement swaps

the X and Z axes

• Result: effective X-basis measurement

• | ۧ+ mapped to | ۧ0• | ۧ− mapped to | ۧ1

Qiskit Terra: more tricks with circuits

• The draw function can use matplotlib, LaTeX, or ASCII art

• Other features: width, depth, and other properties

• More: tutorial 4 in qiskit-iqx-tutorials/fundamentals

Qiskit Terra: backend providers

• Circuits are run on backends, which are accessed through providers

• Standard providers:▪ Aer (local simulators)

▪ IBMQ (IBM devices and simulators)

• Provider features:▪ List and filter available backends

▪ Provide backend objects

▪ IBMQ special function: least_busy

returns backend from the specified list

that has the shortest queue


Qiskit Terra: backend details

• Retrieve configuration details (static):

• Retrieve qubit and gate properties (typically updated daily):

Qiskit Terra: executing a circuit

• execute makes it easy to run a set of circuits on any backend

• Optional arguments▪ memory: if True, return outcome of each individual shot in addition to aggregate counts

▪ initial_layout: manually specify mapping of circuit qubits onto physical qubits

▪ optimization_level: integer from 0 to 3 indicating how aggressively to optimize circuits

▪ See tutorial 5 in qiskit-iqx-tutorials/fundamentals for more options/details

• execute returns a job object immediately after submitting the job to the backend


Qiskit Terra: what execute actually does

▪execute does a lot behind the scenes:

• Verify circuit(s) can run on backend given its

number of qubits and coupling map

• Rewrite operations in terms of backend’s

defined basis gates

• Optimize mapping of circuit onto device

• Minimize number of swaps

• If desired, choose “best” qubits/gates

• Simplify gate sequences

• Submit compiled circuits to backend

Original Compiled

Compilation steps can be customized: see tutorial 4 in qiskit-iqx-tutorials/advanced/terra

• Check job ID, status, and queue position:

• Can also cancel jobs if desired

e.g. bell_job.cancel()

• Job ID can then be used to retrieve job

from backend at any later time:

• Alternatively, if job ID is lost, past jobs

can be retrieved in bulk:

Qiskit Terra: working with jobs

• After job finishes, get results and plot histogram of outcomes

• Strong correlation seen for

both choices of basis, a

signature of entanglement

Qiskit Terra: viewing results

More plotting options: tutorial 2 in qiskit-iqx-tutorials/fundamentals

Note on bit ordering: qubit 0 is

the right-most qubit!

Terra

Aqua

Aer

Qiskit Ignis





Ignis

Qiskit Ignis: Features

• Characterization▪ Coherence (T1 and T2)

▪ Gates (amplitude and angle calibrations)

▪ Hamiltonian (ZZ crosstalk measurement)

• Mitigation▪ Measurement error mitigation

• Verification▪ Quantum volume

▪ Randomized benchmarking

• Tomography (state and process)

Qiskit Ignis: example (error mitigation)

• Challenge: algorithm results are corrupted by SPAM errors

• Mitigation: systematic measurement errors can be calibrated out

• Ignis makes this easy!

Noisy results = A * (Ideal results)

Ideal results = A-1 * (Noisy results)

GHZ state


AquaIgnis

Terra Aer

Qiskit Aer





Qiskit Aer

• High-performance C++ simulator framework

▪ Provides backends to Qiskit Terra

• Simulator backends:

▪ Shot-by-shot QASM simulation (“qasm_simulator”)

▪Quantum state vector calculation (“statevector_simulator”)

▪Unitary operation calculation (“unitary_simulator”)

• Can incorporate noise:

▪Actual error rates

▪ Custom

Qiskit Aer: use in quantum volume studies

• Quantum volume experiments: run random circuits with specific form, compare observed to “expected” outcomes

• Definitions of “expected”:▪ State-vector calculation

▪ Shot-by-shot simulation

– Assuming ideal gates

– Using noise model based

on reported 1Q/2Q errors

• Questions of interest:▪ How do different types of errors

affect success probability?

▪ To what extent does noisy sim

capture actual device behavior?

IBM Q “Tokyo”

success threshold

Cross et al., arxiv:1811.12926

Quantum volume success probabilities:

experiment vs ideal and noisy simulations

Terra Aer

Ignis

Qiskit Aqua





Aqua

Qiskit Aqua

• High-level, application-specific modules

• Interfaces with domain-specific packages e.g. PySCF for chemistry

• Implements hybrid classical-quantum algorithms such as VQE

Qiskit on GitHub and PyPI

• All source code lives within github.com/Qiskit

• Key repositories:Core components (python packages)

▪ qiskit-terra, qiskit-ignis, qiskit-aer, qiskit-aqua: the four elements

▪ qiskit-ibmq-provider: the IBMQ provider for working with IBM backends

▪ qiskit: a metapackage including all of the above

Educational materials (Jupyter notebooks)

▪ qiskit-iqx-tutorials: a “standard” set of instructional Jupyter notebooks

▪ qiskit-community-tutorials: a wider variety of instructional Jupyter notebooks

▪ qiskit-textbook: an open-source quantum computing textbook using Qiskit

• pip install qiskit installs the latest Qiskitmetapackage release from PyPI

https://github.com/qiskit/

Qiskit.org

• A portal to everything Qiskit

• Lots of helpful info at qiskit.org/documentation/

https://qiskit.org/documentation/

Tour of IQX Platform


quantum-computing.ibm.com

Dashboard


Backend detail view



Documentation and support


Circuit composer: quantum score GUI


Circuit composer: QASM editor


Circuit composer: visualizations



Jupyter notebook environment


Start a new notebook from scratch – or import one!

Creating a notebook


• First cell is pre-populated with commonly-used stuff

Useful tricks


• Backend overview

• Backend details

• Job watcher

What’s next

• “Homework”:▪ Create an IQX account

o quantum-computing.ibm.com

▪ Visit ibm.biz/explore_qiskito Create a GitHub account if you don’t already have one

▪ Select a listed topic, or come up with your own

▪ Start looking for 2 – 3 partners to work witho Post your topic as an “issue” in the WiSQCE repository linked from the project list, or join an existing topic

already posted there (i.e. “Assign yourself”)

o If more than 4 people are interested in a single topic, split into two groups!

• Plan for tomorrow:▪ 1:30 – 3:30pm: hands-on programming in small groups

▪ 3:30 – 4:00pm: coffee break

▪ 4:00 – 4:15pm: finish up and prepare to share

▪ 4:15 – 5:00pm: present your team’s findings to the rest of the group

https://quantum-computing.ibm.com/

http://ibm.biz/explore_qiskit

QUESTIONS / DEMO

Programming Quantum Computers with Qiskit and Qiskit...• Define quantum registers • Build quantum circuits • Compile circuits to run on desired backend • Submit jobs (in Qobj

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