CHAPTER 3

Building a Quantum Computer

Written by Mumtaz Gababa, Karthik Narayanan, Elias Lehman, and Alexa Ramirez
In Partnership with Quantum Computing at Berkeley

SECTION 1

Universal Quantum Computing - DiVincenzo’s Criteria

To build a gate-based quantum computer, a set of criteria must be achieved. DiVincenzo’s criteria, proposed by theoretical physicist David P. DiVincenzo, explains the physical implementation requirements for quantum computers, which include a set of conditions that have to be met to achieve a practical computation. The criteria are the following:

 

  1. A scalable physical implementation of the qubits without significantly increasing the complexity of the hardware.
  2. Quantum mechanical systems with two well-defined stable states are used as qubits.
  3. Long coherence times to maintain the quantum state of the system for a sufficient period to perform specific computations.
  4. A universal set of quantum gates.
  5. A qubit-specific measurement capability to obtain the state of the qubit with a low error correction.

To meet these criteria, a quantum computing architecture must be able to manipulate and control individual qubits, perform operations on them using universal gates, correct errors that may occur during computation, and be able to scale up to large numbers of qubits by suitably connecting them. Meeting these criteria is the primary challenge for researchers, forcing them to develop novel approaches that can achieve these requirements.

SECTION 2

Different Ways to Quantum Computers

There are several methods for building a quantum computer, each with its advantages and challenges. A common feature of these methods is that they are all designed around the use of qubits. The most suitable approach to building a quantum computer depends on the specific goals of the manufacturer, which determines what form of qubits to use, and thus the overall structure.

SECTION 3

Electron Spins and Semiconductors

SECTION 4

Superconducting

SECTION 5

Trapped Ion

“The combination of control, stability, scalability, and long coherence time makes the trapped ion model a promising platform for building large-scale quantum computers.”

SECTION 6

Photonic

SECTION 7

Neutral Atom

SECTION 8

Topological

SECTION 9

Industry Timeline

Index

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