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Monday, June 14, 2021

Quantum Heat

 Heat and quantum computing.  Quantum Computing requires physical machines which will need  heat management.  And that such machines may be quite 'delicate' when they erase information.  Shows we have much to do before we have completely general quantum computing.  Technical.  Well worth a read for a prospective practitioner.   Implies these are real considerations for the practical engineering of such systems.

Taking the Heat  By Marina Krakovsky    in the ACM

Communications of the ACM, June 2021, Vol. 64 No. 6, Pages 18-20  10.1145/3460214

Quantum computing, which promises to harness the special properties of quantum mechanics to dramatically speed up calculations and thus help solve currently intractable problems, has attracted considerable investment from tech giants like Google, Microsoft, and IBM. Yet there is still no commercially available quantum computer because of the immense challenges in creating and running such a machine.

One of the major challenges is heat management. As with classical computing, quantum computing uses physical hardware and, therefore, is subject to the laws of physics, particularly the thermodynamics of computation. However, quantum computers are far more fragile than classical computers, requiring far lower temperatures to work properly. Also, as shown in a theoretical paper published in October 2020, the thermodynamics of quantum information processing can create highly unusual and potentially damaging effects for these delicate machines.

The paper, describing a study by researchers at the U.K.'s University of Manchester and Trinity College Dublin, models mathematically what happens when information gets erased in a quantum regime. All erasures cause some heat dissipation, as expected—but to their surprise, the researchers found that every once in a while, the heat dissipated from an erasure is extremely high. In uncovering the potential for such rare but high-impact events, the study suggested something about the future of quantum computing hardware: that it may have to use reversible logic, which by definition does not require erasure of information.

The research also brought back to the fore a famous paradox in thermodynamics that has intrigued scientists since the 19th century—and also a 20th-century insight into the relationship between information and heat, which not only resolved that paradox, but also has practical implications today.  ... "       (links to a number of related technical  papers) 

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