David Elieser Deutsch (; born 18 May 1953) is a British physicist at the University of Oxford. He is a Visiting Professor in the Department of Atomic and Laser Physics at the Centre for Quantum Computation (CQC) in the Clarendon Laboratory of the University of Oxford. He pioneered the field of quantum computation by formulating a description for a quantum Turing machine, as well as specifying an algorithm designed to run on a quantum computer. He has also proposed the use of entangled states and Bell’s theorem for quantum key distribution
and is a proponent of the many-worlds interpretation of quantum mechanics.In 2009, Deutsch expounded a new criterion for scientific explanation, which is to formulate invariants: ‘State an explanation [publicly, so that it can be dated and verified by others later] that remains invariant [in the face of apparent change, new information, or unexpected conditions]’.
“A bad explanation is easy to vary.”
“The search for hard-to-vary explanations is the origin of all progress”
” That the truth consists of hard-to-vary assertions about reality is the most important fact about the physical world.”

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