PHY100 ─ Quantum Computing

Background: The possibility of quantum computation started as early as 1982 by Richard Feynman who was thinking about simulating quantum objects by quantum methods. But the credit is usually given to Paul Benioff who first applied quantum theory to computers in 1981, and to David Deutsch who published a theoretical paper in 1985 describing a quantum computer.

Moore’s Law: The amount of information storable on a given amount of silicon has roughly doubled every 18 months. The trend states that the quantum level will be reached around 2010 ~ 2020.

Quantum Computing: The current theoretical use of quantum physics in the processing and memory functions of computing. Certain properties of atoms or nuclei could allow the processing and memory functions to cooperatively function. These quantum bits, or qubits, would be the computer's processor and memory. The operating speed of qubits is much faster than current technologies permit.


Today’s Computers – memory is made up of bits, each bit holds a one or a zero / Encode information into “bits” using binary numbers, 0 or 1, and can only do calculations on one set of numbers at a time.
Quantum Computers – maintains sequence of qubits, and each qubit can hold a one, a zero, or a superposition of both. It can be both zero and one at the same time. / Encode information according to quantum mechanical states of the involved atomic parts, such as spin directions of electrons or the orientation of photons.

Where qubits can be simultaneously one and zero, is where quantum computers can exponentially reduce the time needed in solving huge problems. Where a classical computer would take 5 trillion years to factor a 5,000 digit number, a quantum computer could finish in 2 minutes. Quantum computation is more powerful than classical computation because more can be computed in less time.

Practical Uses: Cryptography (code cracking), modeling of data, and the indexing of very large databases.

  • Quantum computers are not expected for at least another decade or two

"Quantum Computers". 2005. December 8 2008. <>.