Category Physics

The shape and polarization of a conventional laser beam from a laser pointer mimics quantum entanglement when the laser beam has a polarization dependent shape. This can be used to encode twice as many bits of information as when the laser beam is “separable.” Credit: Giovanni Milione

In a classic eureka moment, a team of physicists is showing how beams from ordinary laser pointers mimic quantum entanglement with the potential of doubling the data speed of laser communication. Described by Albert Einstein as “spooky action at a distance,” when two quantum things are entangled, if one is ‘touched’ the other will ‘feel it,’ even if separated by a great distance.

“At the heart of quantum entanglement is ‘nonseparability’ — two entangled things are described by an unfactorizable equation,” sai...

“Device” is a disc 250 nm in diameter that is capable of switching optical pulses at femtosecond rates (femtosecond is a one millionth of one billionth of a second). Credit: Maxim Scherbakov et al

Researchers developed an ultrafast all-optical switch based on nonlinear dielectric silicon nanostructures. The operation of the switching is based on the interaction between 2 femtosecond pulses; at the same time, the undesirable free-carrier effects are suppressed. Ultrafast optical switching will permit to create data transmission and processing devices which will handle speeds high enough to download 1000s of HD-movies/sec.

Photons address the data transmission problem better than electrons...

The researchers, led by University of Cambridge, used ultrafast laser pulses to observe how a photon, can be converted into 2 energetically excited particles, known as spin-triplet excitons, through a process called singlet fission. If the process of singlet fission can be controlled, it could enable solar cells to double the amount of electrical current that can be extracted.

In conventional semiconductors such as silicon, when 1 photon is absorbed it leads to the formation of 1 free electron that can be harvested as electrical current. However certain materials undergo singlet fission instead, where the absorption of a photon leads to the formation of 2 spin-triplet excitons...