Impossibility of creating a superposition of unknown quantum states

• URL: http://arxiv.org/abs/2011.02275v2
• Date: Tue, 24 Nov 2020 07:13:00 GMT
• Title: Impossibility of creating a superposition of unknown quantum states
• Authors: Somshubhro Bandyopadhyay
• Abstract summary: We show that the existence of a protocol that superposes two unknown pure states with nonzero probability leads to violation of other no-go theorems. Such a protocol can be used to perform certain state discrimination and cloning tasks that are forbidden in quantum theory.
• Score: 16.467540842571328
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: The superposition principle is fundamental to quantum theory. Yet a recent no-go theorem has proved that quantum theory forbids superposition of unknown quantum states, even with nonzero probability. The implications of this result, however, remain poorly understood so far. In this paper we show that the existence of a protocol that superposes two unknown pure states with nonzero probability (allowed to vary over input states) leads to violation of other no-go theorems. In particular, such a protocol can be used to perform certain state discrimination and cloning tasks that are forbidden not only in quantum theory but in no-signaling theories as well.

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