Quantum Computers: A Brief Overview Merciadri Luca
[email protected] Abstract. A promising technology is the “quantum computers,” and this paper gives a general overview about this subject. Keywords: quantum computers. 1 Introduction c being a number. [10] If c = φ ψ the complex con- jugate is h | i A promising technology is the “quantum computers.” c∗ = φ ψ ∗ = ψ φ . (2) More and more scientists are interested in it because h | i h | i The state of a physical system is identified with of the performances’ enhancement it could bring to a ray in a complex separable1 Hilbert space, denoted the today’s computing world. by , or equivalently, by a point in the projective Quantum computers require quantum logic, which HilbertH space of the system. [14] is fundamentally different to classical Boolean logic. Each vector in the ray is called a “ket.” Evidently, This difference leads to a greater efficiency of quan- in the ket ψ , ψ can be replaced by any symbols, let- tum computation over its classical counterpart. [13] ters, numbers,i or even words. The ket can be viewed However, many articles about quantum comput- as a column-vector and (given a basis for the Hilbert ers are still a bit difficult to understand for the “abso- space) written out in components, lute beginner.” Thus, the main aim of this paper is to give a simple overview, without coming into technical ^ ψ = (c , c , ), (3) details, of quantum computing, basing principally on | i 0 1 · · · [3,9,10,13]. when the considered Hilbert space is finite- dimensional.