Schrodinger's sheep. Quantum cloning
Article Abstract:
Pati and Braunstein have argued that deletion of unknown quantum states is not possible, complementing the 'no-cloning theorem'. The distinction between outright erasure and deletion is that erasure is thermodynamically irrevesible. Deletion is logically reversible with no thermodynamic cost. Controlled not (C-NOT) is used to rest the copy bit to O, and C-NOT is logically reversible. Quantum C-NOTs exist and are reversible. Pati and Braunstein have shown that the problem with deleting is similar to that with cloning.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 2000
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Laboratory simulation of cosmic string formation in the early Universe using superfluid 3He
Article Abstract:
The formation of vortices in liquid helium (He) by its transitions into a superfluid state is analogous to the formation of cosmic strings due to symmetry breaking after the Big Bang. Liquid He is heated above the superfluid transition temperature by an exothermic neutron-induced nuclear reaction. The deficit in the amount of energy released as the He cools is a measure of the density of the vortex formed. The results of the study agree with those predicted by Zurek's modification of the Kibble mechanism.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1996
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The shards of broken symmetry
Article Abstract:
The breaking of symmetry in superfluid helium-3 (He-3) and the formation of defects is used to model the dynamics of cosmological phase transitions. Superfluid He-3 is heated and rapidly cooled to make it non-superfluid. Below the critical temperature, the symmetry of He-3 is broken. A gradient in the phase produces a flow pattern whose energy defines the superfluid analogues of cosmic strings, vortex lines. Superfluids are a good medium for studying the defects caused by symmetry breaking.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1996
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