Week 21 - my notes

Week 21 - Quantum Computing Hardware
Resources

Week 21 - Quantum Computing Hardware

How are circuits implemented?

Transpilation
Gates as Pulses
Readout
Display

Transpilation

We want very diverse languages, but not at hardware level
Sometimes you can’t actually apply some gate, because your hardware doesn’t have it, but it can substitute it by two or more gates that can do the same function
It’s like in a map, where the easiest way is to go in a straight line, but there are things on your way (buildings, cars, etc). So you need solutions to do the same things
E.g.: You apply a H gate, but in reality, you apply an RZ gate, a square root X gate, an RZ gate.
IBM is working on transpilation a lot

Gate as Pulses

The gates in your circuit get converted to a sequence of energy pulses
Different gates are implemented as pulses of different duration and energy

Readout

We make a measurement after all gates have been implemented
The measurement pulse is like one

Quantum Hardware

There are two general parts

The quantum chip
All the other components that protect it

Noise and errors

Qubits lose information in two ways: relaxation, decoherence
The first is called T1, and it represents a loss of energy. Qubits want to be in their lowest energy state
The second is called T2, and it represents a loss of energy and of phase. Qubits lose their quantum state due to noise

Errors in measurement

To measure qubits, we have to temporarily open up to the environment

Looking forward

NISQ: “Noisy Intermediate-Scale Quantum devices” It’s like the QASM simulator.The era of error correction. We are here.
Fault-tolerance: It’s like the statevector simulator. An ideal quantum device. We wanna get here to implement our stuff

Resources

Qiskit textbook pages on Measurement Errors and Quantum Error Correction Measurement errors: https://qiskit.org/textbook/ch-quantum-hardware/measurement-error-mitigation.html Quantum Error Correction: https://qiskit.org/textbook/ch-quantum-hardware/error-correction-repetition-code.html

Quantum Computing in the NISQ Era and Beyond URL: https://arxiv.org/abs/1801.00862 Description: Paper by Prof. John Preskill discussing the outlook for quantum computing

Quantum Error Correction: An Introductory Guide URL: https://arxiv.org/abs/1907.11157 Description: Into to QEC techniques