quantum computern. A computer that exploits the quantum mechanical properties of subatomic particles to allow a single operation to act on a large amount of data.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.quantum computer n (Computer Science) a type of computer which uses the ability of quantum systems to be in many different states at once, thus allowing it to perform many different computations simultaneously Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014