Breaking the limits of purification: Postselection enhances heat-bath algorithmic cooling

Abstract

Quantum technologies require pure states, which are often generated by extreme refrigeration. Heat-bath algorithmic cooling is the theoretically optimal refrigeration technique: it shuttles entropy from a multiparticle system to a thermal bath, thereby generating a quantum state with a high degree of purity. Here, we show how to surpass this hitherto-optimal technique by taking advantage of a single binary-outcome measurement. Our protocols can create arbitrary numbers of pure quantum states without any residual mixedness by using a recently discovered device known as a quantum switch to put two operations in superposition, with postselection certifying the complete purification.

11 pages, 3 figures, 1 appendix; updated references; close to published version

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Cited by in corpus (7)

• Evading noise in multiparameter quantum metrology with indefinite causal order
• Reassessing thermodynamic advantage from indefinite causal order
• Experimentally demonstrating indefinite causal order algorithms to solve the generalized Deutsch's problem
• Activation of thermal states by coherently controlled thermalization processes
• State-independent robust heat-bath algorithmic cooling of nuclear spins
• Correlations in a quantum switch-based heat engine with measurements: A proof-of-principle demonstration
• Optimal Thermalization under Indefinite Causal Order with Identical and Asymmetric Baths