Biologists have recently had cause to wonder whether the molecules they know and love are pulling some quantum trickery while they’re not looking: one of the large proteins that captures light in photosynthesis was observed in several studies apparently using coherence, one of the hallmarks of quantum mechanics, to determine the best possible route for shunting energy through its atoms. Now, further experiments that use lasers to tweak such proteins and observe their response have provided more evidence that this is happening—an exciting indication that the strange laws of quantum mechanics can affect the behaviors of large agglomerations of atoms.
Our own Sean Carroll of Cosmic Variance explained how coherence works when this phenomenon was observed in real plants at room temperature last year: Read More
What’s the News: Anyone who has had their thighs baked by a laptop knows that computing releases heat. And it’s more than a common-sense maxim: physicists have shown that heat released by information processing is bound by a physical law, where a bit of information processed must cause a corresponding rise in temperature. But could quantum mechanics allow computations that actually cool computers down? In a recent Nature paper, researchers describe how this paradox is possible.
D-Wave says its chips use quantum mechanics to solve gargantuan problems.
What’s the News: Quantum computing is so complex an idea that even experts have a hard time telling whether a computer is actually “quantum.” But D-Wave Systems, a startup that’s made news and drawn skepticism over the last four years for claiming to have developed a quantum computer, has just made their first sale, to the defense contractor Lockheed Martin. And recent research shows that despite the suspicions D-Wave has endured, there may be at least something to their claim.
What’s the News: On a quest to discover at what size the kooky quantum physics that governs atoms (teleporting!) gives way to the ho-hum classical physics that governs humans (no teleporting), scientists have shown that if conditions are right, a molecule of a record 430 atoms can be in two states at once, like Schrödinger’s infamous cat. For the last three decades, researchers have been watching progressively larger objects under special conditions to see how big of an item they can catch showing quantum behavior. This molecule, which was created by a team at University of Vienna and their collaborators for the experiment, is the largest on record.
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.
It’s one of Stephen Hawking‘s most famous hypotheses (though one often co-credited to other researchers): According to the rules of quantum mechanics, a black hole—from which nothing should be able to escape—actually can emit material in the form of Hawking radiation. In the thirty-plus years since the reknowned physicist made his prediction Hawking radiation has remained theoretical, but a research team now claims to have seen it right in the lab.
First, a quick refresher on Hawking radiation:
Physicists have long realised that on the smallest scale, space is filled with a bubbling melee of particles leaping in and out of existence. These particles form as particle-antiparticle pairs and rapidly annihilate, returning their energy to the vacuum. Hawking’s prediction came from thinking about what might happen to particle pairs that form at the edge of a black hole. He realised that if one of the pair were to cross the event horizon, it could never return. But its partner on the other side would be free to go. [Technology Review]
The lonesome, unpaired particles streaming away would make it appear that the black hole was emitting radiation, Hawking argued.
Physicists have designed the world’s smallest refrigerator, small enough that it can’t hold any of your food. The fridge consists of three qubits–quantum particles that act as on-off switches. These quantum particles could be ions, atoms, or subatomic particles.
Other small systems have been created, but this is the first that doesn’t rely on external mechanisms, such as sophisticated lasers. “The whole guts of the fridge, it’s all accounted for and not hidden in some macroscopic object which is really doing the work,” [coauthor Noah] Linden says. [Science News]
Kitchen refrigerators work by shuttling heat away from one area (where you store your food) and dumping it somewhere else (the coils behind). This transfer isn’t news. Fans of thermodynamics have built devices to wick away heat from one source and dump it somewhere else since the nineteenth century. The device proposed in a paper to appear in Physical Review Letters uses the same basic technique but at a much smaller scale–on the size of three qubits, connected to two “baths,” one cold (or around room temperature) and one hot.
In a study published yesterday in Science, physicists describe their attempts to study the overlap between these two theories–by dropping really cold rubidium (only billionths of a degree warmer than absolute zero) from a great height (480 feet). The cold rubidium behaves as an observable, quantum mechanical system and since gravity is a main driver in general relativity, watching gravity’s pull on that system might give researchers glimpses into how to tie the two theories together.
“Both theories cannot be combined,” said researcher [and coauthor of the paper] Ernst Rasel of the University of Hannover in Germany. “In that sense we are looking for a new theory to bring both together.” [Live Science]
Here’s what they did:
Step 1 — Cool it
Physicists first made super-cold Bose-Einstein condensates of rubidium. Since heat is really the random jostling of molecules, to cool things down, experimenters had to make those molecules sit still. They used an elaborate system of lasers to hold the molecules steady.
When rubidium atoms get that cold, they exhibit quantum mechanical behaviors that researchers can observe, acting like one giant particle-wave.
The idea is to chill a cluster of atoms to a temperature that is within a fraction of absolute zero. At that extreme, the atoms all assume the same quantum-mechanical state and begin to behave collectively as a sort of super-atom, known as a Bose-Einstein condensate (BEC). [Nature News]
In this study, researchers contained that complicated system in a two-foot diameter and seven-foot tall cylinder.
A 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.
The strange quantum state of entanglement isn’t just challenging to think about, it’s hard to create. This “spooky” phenomenon—in which two particles are linked, even if they’re separated by distance—can be created by scientists in the lab using bulky lasers. But scientists published a study in Nature today in which they created a light-emitting diode (LED) that produces entangled photons.
One reason entanglement is exciting is the potential to drive quantum computers that make today’s best look pokey by comparison, like so:
Quantum computers exploit the inherent uncertainties of quantum physics to perform calculations much faster than computers currently in use. Whereas conventional ‘bits’ of information take only the values zero or one, quantum bits, or ‘qubits’, exist in a fuzzy superposition of both. In theory, this ambiguity allows any number of qubits to be lumped together or ‘entangled’ and processed in parallel, so that a huge number of calculations can be made at once [Nature].
That’s great in theory, but the standard practice for making entangled particles is unwieldy and unreliable, according to team member Mark Stevenson of Toshiba: