# Technologies

## Optical Method for Quantum Computing

### Reference#: P01371

Many kinds of numerical problems cannot be solved using conventional computers because of the time required to complete the computation. It has been estimated that the time required to factor a 150-digit number using the fastest supercomputers currently available would be longer than the age of the universe. Future increases in the speed of conventional computers will clearly be inadequate for problems of that kind, which are often of considerable practical importance. It has been shown that quantum-mechanical computers could use non-classical logic operations to provide efficient solutions to certain problems of that kind, including the factoring of large numbers. The operation of individual quantum logic gates has been demonstrated, but no operational quantum computer has been constructed.

The Johns Hopkins Applied Physics Lab has invented a novel optical method for quantum computing that makes use of non-local effects to construct the quantum gates themselves. A non-local interaction in which pairs of atoms interchange two photons produces a large nonlinear phase shift. These nonlinear phase shifts are used to construct quantum logic gates, such as a Controlled-NOT.

In addition to performing non-classical logic operations, quantum computers will be able to perform a large number of different calculations simultaneously on a single processor, which is clearly not possible for a conventional computer.

**CONTACT:**

Dr. G. R. Jacobovitz

Phone: (443) 778-9899

ott-techmanager3@jhuapl.edu