Synopsis: Multiple entanglements

Researchers report entanglement of many cavity modes using an optical frequency comb.
Synopsis figure
Credit: M. Pysher et al., Phys. Rev. Lett. (2011)

Quantum computers might one day allow exponential speedups in tasks such as large-integer factoring, but there is a price: the need to precisely control and coordinate many fragile qubits in a series of error-free steps. Among the proposals for achieving this, one “top-down” architecture relies on the normal modes of an optical system (think of a set of quantum harmonic oscillators) to act as qubits. The trick is to create and manipulate entanglement of these modes, called Qmodes, in ways suitable for information processing. In a paper in Physical Review Letters, Matthew Pysher at the University of Virginia, US, and colleagues now report the largest collection of Qmodes to date and suggest how the technique might be scaled to encompass more.

To generate the Qmodes, the authors use an optical parametric oscillator, a device with the handy ability to take a single photon as input and emit two entangled photons. The parametric oscillator can be driven to create an optical frequency comb, which is a series of Qmodes separated by known frequencies and precisely related to each other in phase. Pysher et al. were able to engineer 15 groups of four entangled Qmodes each, for a total of 60. However, this was only the number of entangled modes they could measure; the authors believe that substantially more modes, perhaps as many as 150 groups, were actually created. With this result, the authors hope to set a course for massive entanglement of many modes into a single group, a prerequisite for any all-optical quantum computer. – David Voss

Note added (19 July 2011): The text has been revised to reflect the fact that Pysher et al. study continuous-value modes (Qmodes) and not qubits (quantum binary digits).


Features

More Features »

Announcements

More Announcements »

Subject Areas

Quantum Information

Next Synopsis

Strongly Correlated Materials

Majorana states thrive under interactions

Read More »

Related Articles

Synopsis: Superdense Coding over Optical Fiber
Quantum Information

Synopsis: Superdense Coding over Optical Fiber

Researchers have demonstrated the fiber transmission of quantum information in which each quantum bit carries nearly two bits of classical information. Read More »

Synopsis: Quantum Signals Outpace Classical Ones
Quantum Information

Synopsis: Quantum Signals Outpace Classical Ones

New theoretical work shows how much faster quantum information can travel through a system than classical information. Read More »

Synopsis: Quantum Circulator on a Chip
Quantum Information

Synopsis: Quantum Circulator on a Chip

A circulator that routes microwave signals is suitable for scaling up quantum-computing architectures. Read More »

More Articles