Seminari di gruppo IV

Quantum computing in Plato’s cave

by Prof. Paolo Facchi (Università di Bari)

Europe/Rome
1G09 (M. S. Angelo)

1G09

M. S. Angelo

Description
We show that the mere observation of a quantum system can turn its dynamics from a very simple one into a universal quantum computation. This effect, which occurs even if a small part of the system is regularly observed, can be rephrased as a modern version of Plato's Cave allegory. More precisely, in the original version of the myth, the reality perceived within the Cave is described by the projected shadows of some more fundamental dynamics (the Ideals) which is intrinsically more simple (intelligible). We found that in the quantum world the ``projected'' reality perceived through measurements is even more complex than in a classical world. After discussing examples we go on to show that this effect is generally to be expected: almost any quantum dynamics will become universal once observed as outlined above. Moreover, the same effect is obtained just from a local noise. Conversely, we show that any complex quantum dynamics can be purified into a simpler one in larger dimensions.