Tag: quantum entanglement

Two Diamonds Get Quantum Entangled, Physicists Report

By Veronique Greenwood | December 2, 2011 2:17 pm

Atoms are governed by the strange laws of quantum physics—they can communicate across long distances, teleport, and perform myriad other acts that sound straight out of science fiction. But although we’re made up of atoms, we can’t do any of that stuff. We’re governed by the laws of classical, or Newtonian, physics, where there’s no teleporting allowed.

How many atoms have to get together for classical physics to take over? Many physicists would dearly like to know, and, in an effort to suss out just when the change-over happens, have set up numerous experiments in which they watch for signs of quantum behavior in ever-larger objects, from molecules to nanoscale slivers of metal. But a paper published this week in Science takes the cake. Researchers report that they have observed entanglement in two three-millimeter-wide diamonds. Read More


Physicists Find New Way to Store Quantum Information in Impure Diamonds

By Valerie Ross | March 28, 2011 4:39 pm

What’s the News: Physicists have worked out a new method of storing information in the quantum states of atoms in diamond crystals. The scientists linked the spin of individual nitrogen atoms in the diamond—impurities at the jewelry counter, but boons in the physics lab—to the spin of nearby electrons. They could form a quantum link between the spin of the nitrogen atom and the spin of a nearby electron, letting the electron store information more stably than if it were spinning on its own.

How the Heck:

  • When a nitrogen is next to an empty spot in a diamond’s carbon framework, it lets off an extra electron, leaving that electron free to have its quantum played around with.
  • Using what they call “intense microwave fields” [PDF], the physicists were able to link the spin of a nitrogen atom to a neighboring electron, a pairing sparked by magnetic fields.

What’s the Context:

  • Scientists have been looking at diamonds—with and without nitrogen impurities—as a quantum computing material for several years, in part because it can store quantum memory at room temperature, not the far-below-freezing temps required by some other materials.
  • Some have even proposed the idea of diamond supercomputers, which would store millions of times as much data as today’s machines.
  • One hurdle in quantum computing is getting the information to last long enough to use it. In the recent study, the nuclear spin stayed coherent for more than a millisecond—enough time for a ten petaflop supercomputer to do ten trillion operations.

Not so Fast:

  • Don’t start rooting around in your hard drive for a rock just yet; diamond-based quantum computing is still a long way off.

Reference: “Quantum control and nanoscale placement of single spins in diamond.” David D. Awschalom, invited talk, American Physical Society March Meeting 2011

Image: Flickr / Swamibu


A Step Towards Quantum Computing: Entangling 10 Billion Particles

By Patrick Morgan | January 19, 2011 6:37 pm

In life, most people try to avoid entanglement, be it with unsavory characters or alarmingly large balls of twine. In the quantum world, entanglement is a necessary step for the super-fast quantum computers of the future.

According to a study published by Nature today, physicists have successfully entangled 10 billion quantum bits, otherwise known qubits. But the most significant part of the research is where the entanglement happened–in silicon–because, given that most of modern-day computing is forged in the smithy of silicon technology, this means that researchers may have an easier time incorporating quantum computers into our current gadgets.

Quantum entanglement occurs when the quantum state of one particle is linked to the quantum state of another particle, so that you can’t measure one particle without also influencing the other. With this particular study, led by John Morton at the University of Oxford, UK, the researchers aligned the spins of electrons and phosphorus nuclei–that is, the particles were entangled.

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CATEGORIZED UNDER: Physics & Math, Technology

Can Physicists Make Quantum Entanglement Visible to the Naked Eye?

By Joseph Calamia | June 6, 2010 12:02 pm

handsA pair of quantum entangled photons sure makes a cute couple. Of course, the two might have opposite states–one might be spin up and another spin down, for example–but they promise they’ll always stay that way.

They’re also fiercely loyal, respecting their opposite-spin preferences no matter how long-distance their relationship. (That means that by checking the state of one entangled photon, you can instantly know the state of the other, distant photon, a handy way to “teleport” information.) Unfortunately, because the couple is merely two light particles, their shining example of old romance has been too dim for our eyes to see.

Until now. As announced in their recently published Arxiv.org paper, physicists led by Nicolas Gisin at the University of Geneva in Switzerland believe they have found a way to watch this love affair unfold: by boosting the light emitted by one member of a quantum entangled pair, they think they can make this quantum effect visible to a human eye.

Measuring quantum states such as spin up or spin down is like looking at whether a switch is on or off. This closely matches the concept of a bit, a single 1 or 0, in computing. With entangled photons, physicists call these on/off states quantum bits or “qubits.” What an observer would see while observing an entangled photon is really a choice between two states. The observer could then confirm entanglement by checking to see that the photon was loyal to its partner.

In the traditional set-up, two widely separated particle detectors are used to measure the entanglement of the two photons. But Gisin and his colleagues want to let the human eye do some of the work.

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