Quantum machine Quantum machine A quantum machine is a human-made device whose collective motion follows the laws of quantum mechanics. The idea that macroscopic objects may follow the laws of quantum mechanics dates back to the advent of quantum mechanics in the early 20th century. However, as highlighted by the Schrödinger's cat thought experiment, quantum effects are not readily observable in large-scale objects. Consequently, quantum states of motion have only been observed in special circumstances at extremely low temperatures. The fragility of quantum effects in macroscopic objects may arise from rapid quantum decoherence. Researchers created the first quantum machine in 2009, and
Expectation value (quantum mechanics) A particularly simple case arises when formula_1 is a projection, and thus has only the eigenvalues 0 and 1. This physically corresponds to a "yes-no" type of experiment. In this case, the expectation value is the probability that the experiment results in "1", and it can be computed as (3) formula_24. In quantum theory, also operators with non-discrete spectrum are in use, such as the position operator formula_25 in quantum mechanics. This operator does not have eigenvalues, but has a completely continuous spectrum. In this case, the vector formula_11 can be written as a complex-valued function formula_27 on the spectrum