Energy could in theory be teleported over any distance, researchers in Japan say. The science team behind the discovery said such quantum energy transfer could help advance quantum computers and shed light on the mysteries of black holes.
Teleporting an object from one point in the universe to another without it traveling through the space in between might sound like part of a Star Trek episode, but scientists have actually been doing it since the 1990s. The current long-distance record for teleportation is roughly 89 miles, a feat that was announced in 2012 between the two Canary Islands of La Palma and Tenerife off the northwest coast of Africa.
The form of teleportation that scientists have practiced for years relies on capturing the fundamental details of an object — its “quantum state” — and transmitting that information from one location to another to recreate the object exactly someplace else. Such quantum teleportation is based on the strange nature of quantum physics, which suggests that the elementary building blocks of the universe can essentially exist in two or more places at once, or spin in two opposite ways simultaneously.
Specifically, quantum teleportation relies on the mysterious phenomenon known as quantum entanglement, in which objects can become linked and influence each other instantaneously regardless of distance. Einstein famously rebelled against the notion of quantum entanglement, derisively calling it “spooky action at a distance,” but scientists have repeatedly proven it works.
The quantum teleportation of, say, an electron, would first involve “entangling” a pair of electrons. Next, one of the two subatomic particles — the one to be teleported — would stay in one place while the other electron would be physically transported to whatever destination is desired. The quantum state of the electron to be teleported is then analyzed and that data is sent in a signal to the destination, where it can be used on the other electron to recreate the first one. Since the signal is sent using classical forms of communication, quantum teleportation can proceed no faster than the speed of light.
Not limited to matter
In 2010, theoretical physicist Masahiro Hotta at Tohoku University in Sendai, Japan, suggested teleportation of energy might be possible as well. Now Hotta and his colleagues reveal that quantum energy teleportation is not limited by distance.
"It is certainly possible in principle," says MIT quantum physicist Seth Lloyd, who did not take part in this research.
The key to understanding quantum energy teleportation lies in a quantum physics revelation that a vacuum is not actually empty, but in fact is fluctuating with energy. If one can imagine that a particle essentially exists in two or more places at once, one might also conceive that virtual particles can pop in and out of existence anywhere, even in vacuum. (Both virtual particles and their antimatter counterparts leap in and out of existence this way, so the net energy of vacuum remains zero.)
Quantum energy teleportation would involve entangling a pair of photons, the elementary particle of electromagnetic radiation. These photons are then separated and placed in two different regions of vacuum, which thus become entangled.
Since vacuum fluctuates with energy, there is a chance that at some point a region of vacuum will have negative energy, resulting in the absorption of energy from the surrounding area. If measurements reveal an entangled vacuum has negative energy, the data announcing this state can then get sent to the other vacuum, where positive energy can be extracted.
"One is not actually sending energy from point A to point B so much as making a measurement at point A that reveals the presence of energy at point B that can be extracted," Lloyd says.
The net amount of energy in the entangled system is always zero — any increase of energy in one vacuum is balanced by a decrease in the other. In addition, like with quantum teleportation of matter, the signal carrying this data can travel no faster than the speed of light.
Extending the bridge
A major problem with quantum energy teleportation was that it only appeared possible over very short distances of tens to hundreds of nanometers, or billionths of a meter. (In comparison, the average diameter of a human hair is about 100,000 nanometers.)
Hotta and his colleagues have discovered a way around this limit.
The key to overcoming this obstacle is creating what are known as squeezed vacuum states. According to quantum physics, one can perfectly measure either the position or the momentum of a particle—but not both variables—with unlimited accuracy, a phenomenon known as Heisenberg’s uncertainty principle. There are other, similar complementary pairs of variables in quantum physics. In a squeezed vacuum state, one can increase the variance of a magnetic field, which reduces the variance of the electric field in that vacuum, with the average values for both kept at zero.
By using squeezed vacuum states instead of regular vacuums, experimental verification of energy teleportation may be much easier. Hotta noted that study coauthor Go Yusa is now planning a quantum energy teleportation experiment and hoping to get it funded. Hotta, Yusa and their colleague Jiro Matsumoto detailed their findings in the January issue of the journal Physical Review A.
As exciting as quantum energy teleportation may sound, it has a number of profound limitations.
"This is not a technology for sending energy from A to B more efficiently," Lloyd says. "This method isn’t powering any spaceship anytime soon. In fact, it’s not even powering a desk lamp."
A major problem with quantum energy teleportation is that there is an apparently equal, random chance of finding negative or positive energy at the vacuum being measured.
"This feature strongly limits the application of the results," Lloyd says. "Probably you remember the old saying, ‘If you want to send a message, call Western Union.’ Here, I’d say, ‘If you want to send energy, use a tanker trailer.’"
In addition, no practical methods currently exist for creating a squeezed vacuum state over any distance longer than a centimeter, Lloyd says. Moreover, while these latest findings suggest energy teleportation can take place over any distance, the amounts of energy that can get teleported remain small. Also, the more energy that is available for teleportation, the smaller the distance it can get transferred.
"The amounts of energy that can be teleported for a long distance, where ‘long’ means more than a micron, are teeny," Lloyd says. Though it might be possible to teleport "tiny amounts of energy inside a tiny quantum circuit."
If scientists can harness quantum energy teleportation, Hotta previously noted it could have impacts on quantum devices such as quantum computers, which could in principle run more calculations in an instant than there are atoms in the universe. Quantum computers depend on entanglement, but stray bits of heat can readily disrupt entanglement, a problem known as thermal decoherence. Teleportation could help rapidly distribute energy within quantum devices without generating unwanted heat.
These findings could also help shed light on how black holes shrink, Lloyd says. Past research suggested that black holes might lose mass by giving off energy. This so-called Hawking radiation emerges from the vacuum around black holes. “The way energy can get teleported is not dissimilar to what happens when you have energy escaping from a black hole, and so quantum energy teleportation could be a way of understanding what’s going on with black holes,” Lloyd says.
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