quantum entanglement tagged posts

43Ca+ qubit states and Raman transitions used for sideband cooling, single-qubit and two-qubit gates. Credit: arxiv.org/abs/1512.04600

The team achieved the logic gate, which places 2 atoms in a state of quantum entanglement and is the fundamental building block of quantum computing, with a precision (or fidelity) substantially greater than the previous world record. Quantum entanglement—a phenomenon described by Einstein as ‘spooky’ but which is at the heart of quantum technologies—occurs when 2 particles stay connected, such that an action on one affects the other, even when they are separated by great distances

The precision of the gate is a measure of how well quantum entanglement works: in our case, 99...

Some measurements of entanglement violate monogamy, yet are geometrically faithful; others are monogamous but not faithful. Credit: Lancien et al. ©2016 American Physical Society

As expected, “monogamous” and “faithful” mean something a little different in the quantum world than they do in everyday language. When quantified by standard means, entanglement cannot be both monogamous and faithful at the same time. The results may be relevant when assessing the security of quantum cryptographic schemes, which rely on the monogamy of entanglement, and may also help to better understand the long-standing “firewall debate” related to the behavior of black holes.

Monogamy is considered to be a defining property of entanglement. Eg...

Paul Klimov, a graduate student in the University of Chicago’s Institute for Molecular Engineering, adjusts the intensity of a laser beam during an experiment. Because the laser light lies within the infrared spectrum, it is invisible to the human eye. Credit: University of Chicago

Entanglement says that 2 particles can be so inextricably connected that the state of one particle can instantly influence the state of the other, no matter how far apart they are. It will be useful for quantum computers, quantum communication networks, and high-precision quantum sensors.
Entanglement is also one of nature’s most elusive phenomena.

Producing entanglement between particles requires that they start out in a highly ordered state, which is disfavored by thermodynamics, the process that governs the i...

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...