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Sunday, 22 November 2015

Scientists Achieve Quantum Entanglement at Room Temperature in Semiconductors

Entanglement is one of the strangest phenomena predicted by quantum mechanics, the theory that underlies most of modern physics. Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently—instead, a quantum state may be given for the system as a whole.

Just one century ago, entanglement was at the center of intense theoretical debate, leaving scientists like Albert Einstein totally perplexed. Today, however, entanglement has been accepted as a fact of nature and is actively being explored as a resource for future technologies including 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 interactions between heat and other forms of energy. This poses a particularly formidable challenge when trying to realize entanglement at the macroscopic scale, among huge numbers of particles.

quantum entanglement lab
Paul Klimov. Photo Credit: University of Chicago

Previously, scientists have overcome the thermodynamic barrier and achieved macroscopic entanglement in solids and liquids by going to ultra-low temperatures (-270 degrees Celsius) and applying huge magnetic fields (1,000 times larger than that of a typical refrigerator magnet) or using chemical reactions.

However, in the November 20th issue of Science Advances, Paul Klimov, a graduate student in the University of Chicago's Institute for Molecular Engineering and other researchers in David Awschalom's group at the Institute for Molecular Engineering demonstrated that macroscopic entanglement can be generated at room temperature and in a small magnetic field.

The researchers used infrared laser light to order (preferentially align) the magnetic states of thousands of electrons and nuclei and then electromagnetic pulses, similar to those used for conventional magnetic resonance imaging (MRI), to entangle them.

This procedure caused pairs of electrons and nuclei in a macroscopic 40 micrometer-cubed volume (the volume of a red blood cell) of the semiconductor SiC to become entangled.

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