How do quantum computers work? An overview

For some time now, research has been going on into a new type of computer, the quantum computer. At the moment, this technology exists only in the laboratory, and this will not change for several years. Yet a quantum computer is very useful, especially for special problems.

How a quantum computer works

A quantum computer is not yet ready for everyday use. However, scientists are continuously working on the technology. IBM has already presented a working computer. A quantum computer works with qubits, which altogether form a quantum register in which information is stored.

1. In an ordinary computer, you work with bits that take the values 0 and 1. However, within a period of time, it is possible for a qubit to be in a state between 0 and 1. This time span is also called coherence time.
2. You resolve this intermediate state of superposition by measuring the qubit. Thus, it can be subsequently stored. This process is again called decoherence.
3. A qubit usually consists of ions or superconducting loops (SQUIDs), where 0 represents an ion with possible lowest energy and 1 represents an ion in excited state.
4. Quantum registers usually consist of 14 ions. With these, the same computational operations can be performed as in an ordinary computer. Hierfür werden die logischen Operatoren verwendet, die bei einem Quantencomputer auch als Quantengatter bezeichnet werden.
5. Beim Quantengitter ist vor allem darauf zu achten, dass diese vor Störeinflüssen geschützt sind, da die Qubits für die Berechnungen ihren Zustand so lange wie möglich halten müssen.