CirQ Quantum programmming

CirQ is a python framework for creating, editing, and invoking Noisy Intermediate Scale Quantum (NISQ) circuits.

Install

python3 -m pip install --upgrade pip
python3 -m pip install cirq 

dependencies

For witing to pdf

brew cask install mactex

Circuis

Can be either

• Circuit Circuit is a collection of Moments. A Moment is a collection of Operations that all act during the same abstract time slice.

• schedule Schedules offer more control over quantum gates and circuits at the timing level

Cirq has three main ways of defining qubits:

• cirq.NamedQubit: used to label qubits by an abstract name
• cirq.LineQubit: qubits labelled by number in a linear array
• cirq.GridQubit: qubits labelled by two numbers in a rectangular lattice.

Variational quantum algorithms

The variational method in quantum theory is a classical method for finding low energy states of a quantum system.

In classical variational method to a system of n qubits, an exponential number (in n) of complex numbers are necessary to generically represent the wave function of the system.

However with a quantum computer one can directly produce this state using a parameterized quantum circuit, and then by repeated measurements estimate the expectation value of the energy.