In quantum computation, information is represented by quantum bits (qubits), which are superpositions of quantum states. Quantum computers can efficiently solve problems that cannot actually be solved by conventional computers operating on existing principles. In order to develop quantum computers with solid-state components, materials with a long coherence time (quantum-state duration) and qubit operations that do not affect the quantum state are essential.
Toshiba has succeeded in operating a single-qubit gate. It is equivalent to the NOT gate in conventional computers, by using the states of nuclear spins of Pr3+ (praseodymium ion) contained in a solid-state electromagnetically induced transparency (EIT) medium (Pr3+: Y2SiO5), which have extremely long coherence time, as the quantum bits, and by applying a special operation method (adiabatic passage with three lights), which does not reduce the coherence time, to the qubits for the first time(*) .
The single-qubit gate constitutes a set of universal gates when combined with a two-qubit gate, which is a conditional gate between two qubits (equivalent to the AND gate in conventional computers). Toshiba aims to realize two-qubit gate operations that will lead to the development of scalable quantum computers using the coupling between qubits and a cavity mode.
(*) In January 2006, and the results were presented at academic conferences, in the press, etc.
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