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 interactions between heat and other forms of energy. “The macroscopic world that we are used to seems very tidy, but it is completely disordered at the atomic scale. The laws of thermodynamics generally prevent us from observing quantum phenomena in macroscopic objects,” said Paul Klimov.
Previously, scientists have overcome the thermodynamic barrier and achieved macroscopic entanglement in solids and liquids by going to ultra-low temperatures (-270C) and applying huge magnetic fields (1,000 times larger than that of a typical refrigerator magnet) or using chemical reactions. Klimov et al in David Awschalom’s group at the Institute for Molecular Engineering have 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 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.
“We know that the spin states of atomic nuclei associated with semiconductor defects have excellent quantum properties at room temperature,” said Awschalom, Liew Family Professor in Molecular Engineering and a senior scientist at Argonne National Laboratory. “They are coherent, long-lived and controllable with photonics and electronics. Given these quantum ‘pieces,’ creating entangled quantum states seemed like an attainable goal.”
The techniques in combination with sophisticated devices enabled by advanced SiC device-fabrication protocols could enable quantum sensors that use entanglement as a resource for beating the sensitivity limit of traditional (non-quantum) sensors. Given that the entanglement works at ambient conditions and SiC is bio-friendly, one particularly exciting application is biological sensing inside a living organism. “We are excited about entanglement-enhanced magnetic resonance imaging probes, which could have important biomedical applications,” said Abram Falk of IBM’s Thomas J. Watson Research Center.
In the long term, it might even be possible to go from entangled states on the same SiC chip to entangled states across distant SiC chips. Such efforts could be facilitated by physical phenomena that allow macroscopic quantum states, as opposed to single quantum states (in single atoms), to interact very strongly with one another, which is important for producing entanglement with a high success rate. Such long-distance entangled states have been proposed for synchronizing global positioning satellites and for communicating information in a manner that is fundamentally secured from eavesdroppers by the laws of physics.
http://phys.org/news/2015-11-quantum-entanglement-room-temperature-semiconductor.htmljCp
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