Quantum Computer

A Quantum Computer is a computing device that makes direct use of quantum-mechanical phenomena (such as superposition and entanglement).

• Context:
  • It can (typically) be composed of Qubits.
  • It can be used to implement a Quantum Algorithm.
• Example(s):
  • a D-Wave Two Computer[1].
  • a D-Wave One Computer.
• Counter-Example(s):
  • a Digital Computer.
• See: Solid State Chip, Analog Computer, D-Wave Systems, Inc..

---

---

References

2016

• CHRISTOPHER MONROE. (2019). "Quantum Computing is a Marathon not a Sprint." APRIL 21, 2019
  • QUOTE: Ordinary computers think in certainties, digitizing every aspect of the world to well-defined numbers. Quantum computers probe all possibilities, constantly updating the probabilities of multiple scenarios. Add more qubits, and they can consider exponentially more scenarios. A quantum computer is programmed to consider all these possibilities and narrow them down to just a few, and then when the output is measured, it can tell us information about all those scenarios. It is critical that a quantum computer not be measured or looked at while it considers the uncountable number of possibilities. For that reason, qubits are like senators before a controversial vote: They shouldn’t reveal their position until they are forced to. ...

    bank might use a quantum computer to estimate how much money you will have in your account a year from now, based on the probability you will get a raise or get fired, whether your teenager will crash the car, if the stock market will crash, and how these factors interact. ...

    In 3-5 years, these machines will perform certain calculations that would not be possible using ordinary computers. But it may be 5-10 years before any of these machines have the capacity and accuracy to solve useful problems. ...

2016

• https://www.theguardian.com/technology/2016/may/22/age-of-quantum-computing-d-wave
  • QUOTE: Rose chose instead to develop an “adiabatic” quantum computer, which works by a process of what’s called “quantum annealing” or “tunnelling”. In essence, it means you develop an algorithm that assigns specific interactions between the qubits along the lines of the classical model – ie if this is a 0, that one is 1 etc. Then create the conditions for quantum superposition, in which the qubits can realise their near infinite possibilities, before returning them to the classical state of 0s and 1s. The idea is the qubits will follow the path of least energy in relation to the algorithmic requirements, thus finding the most efficient answer.

2014

• http://www.dwavesys.com/tutorials/background-reading-series/quantum-computing-primer#h2-0
  • … The fundamental power of a quantum computer comes from the idea that you can put bits of information into a superposition of states. You can think of this as being a situation where the qubit has not yet decided which state it wants to be in. Some people like to refer to the qubit in superposition as 'being in both states at the same time'. ...

2013

• http://en.wikipedia.org/wiki/Quantum_computer
  • A quantum computer is a computation device that makes direct use of quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from digital computers based on transistors. Whereas digital computers require data to be encoded into binary digits (bits), quantum computation uses quantum properties to represent data and perform operations on these data. A theoretical model is the quantum Turing machine, also known as the universal quantum computer. Quantum computers share theoretical similarities with non-deterministic and probabilistic computers. One example is the ability to be in more than one state simultaneously. The field of quantum computing was first introduced by Yuri Manin in 1980 and Richard Feynman in 1981. A quantum computer with spins as quantum bits was also formulated for use as a quantum space-time in 1969.

    Although quantum computing is still in its infancy, experiments have been carried out in which quantum computational operations were executed on a very small number of qubits (quantum bits). Both practical and theoretical research continues, and many national governments and military funding agencies support quantum computing research to develop quantum computers for both civilian and national security purposes, such as cryptanalysis.

    Large-scale quantum computers will be able to solve certain problems much faster than any classical computer using the best currently known algorithms, like integer factorization using Shor's algorithm or the simulation of quantum many-body systems. There exist quantum algorithms, such as Simon's algorithm, which run faster than any possible probabilistic classical algorithm. Given sufficient computational resources, a classical computer could be made to simulate any quantum algorithm; quantum computation does not violate the Church–Turing thesis. However, the computational basis of 500 qubits, for example, would already be too large to be represented on a classical computer because it would require 2⁵⁰⁰ complex values (2⁵⁰¹ bits) to be stored. (For comparison, a terabyte of digital information is only 2⁴³ bits.)

---