Quantum Teleportation

Quantum teleportation was just achieved over more than 7 km of city fibre

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It’s getting real.

Quantum teleportation just moved out of the lab and into the real world, with two independent teams of scientists successfully sending quantum information across several kilometres of optical fibre networks in Calgary, Canada, and Hefei, China.

The experiments show that not only is quantum teleportation very much real, it’s also feasible technology that could one day help us build unhackable quantum communication systems that stretch across cities and maybe even continents.

Quantum teleportation relies on a strange phenomenon called quantum entanglement. Basically, quantum entanglement means that two particles are inextricably linked, so that measuring the state of one immediately affects the state of the other, no matter how far apart the two are – which led Einstein to call entanglement “spooky action at a distance“.

Using that property, quantum teleportation allows the quantum state of one particle to be transferred to its partner, no matter the distance between the two, without anything physical passing between them.

That’s not like the teleportation you see in sci-fi shows like Star Trek – only information can be sent via quantum teleportation, not people.

What it is, though, is a great way to create an unhackable, totally encrypted form of communication – just imagine receiving information that can only be interpreted once you know the state of your entangled particle.

In the latest experiments, both published in Nature Photonics (here and here), the teams had slightly different set-ups and results. But what they both had in common is the fact that they teleported their information across existing optical fibre networks – which is important if we ever want to build useable quantum communication systems.

In fact, quantum teleportation has been achieved over greater distances in the past – in 2012, researchers from Austria set a record by teleporting information across 143 km of space using lasers, but that technology isn’t as useful for practical networks as optical fibre.

To understand the experiments, Anil Ananthaswamy over at New Scientist nicely breaks it down like this: picture three people involved – Alice, Bob, and Charlie.

Alice and Bob want to share cryptographic keys, and to do that, they need Charlie’s help. Alice sends a particle to Charlie, while Bob entangles two particles and sends just one of them to Charlie.

Charlie then measures the two particles he’s received from each of them, so that they can no longer be differentiated – and that results in the quantum state of Alice’s particle being transferred to Bob’s entangled particle.

So basically, the quantum state of Alice’s particle eventually ends up in Bob’s particle, via a way station in the form of Charlie.

The Canadian experiment followed this same process, and was able to send quantum information over 6.2 km of Calgary’s fibre optic network that’s not regularly in use.

“The distance between Charlie and Bob, that’s the distance that counts,” lead researcher of the Canadian experiment, Wolfgang Tittel, from the University of Calgary in Alberta, told New Scientist. “We have shown that this works across a metropolitan fibre network, over 6.2 kilometres, as the crow flies.”

The Chinese researchers were able to extend their teleportation further, over a 12.5 km area, but they had a slightly different set-up. It was Charlie in the middle who created the entangled particles and sent one to Bob, instead of the other way around.

This resulted in more accurate communication, and could work best for a quantum network where a central quantum computer (Charlie) communicates with lots of Alices and Bobs around a city. But the Calgary model could spread even greater distances, because Bob could work like a quantum repeater, sending the information further and further down the line.

The downside to both experiments was that they couldn’t send very much information. The Calgary experiment was the fastest, managing to send just 17 photons a minute.

And while many people assume that quantum teleportation would result in faster communication, in reality, decrypting the quantum state of the entangled particle requires a key, which needs to be sent via regular, slow communication – so quantum teleportation wouldn’t actually be any faster than the internet we already have, just more secure.

But the fact that both teams were able to use existing telecommunications infrastructure to achieve such long-distance teleportation at all is a huge deal – and something that hasn’t been done outside of the lab before.

It’s going to take a lot more tweaking and investigation before it’s something that we can use in our daily lives, but we’re definitely getting closer.

Shades of ‘Star Trek’? Quantum Teleportation Sets Distance Record

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A record-breaking distance has been achieved in the bizarre world of quantum teleportation, scientists say.

The scientists teleported photons (packets of light) across a spool of fiber optics 63 miles (102 kilometers) long, four times farther than the previous record. This research could one day lead to a “quantum Internet” that offers next-generation encryption, the scientists said.

Teleporting an object from one point in the universe to another without it moving through the space in between may sound like science fiction pulled from an episode of “Star Trek,” but scientists have actually been experimenting with “quantum teleportation” since 1998.

Quantum teleportation depends on capturing the fundamental details of an object — its “quantum states” — and instantly transmitting that information from one area to another to recreate the exact object someplace else.

Quantum teleportation relies on the strange nature of quantum physics, which finds that the fundamental building blocks of the universe can essentially exist in two or more places at once.

Specifically, quantum teleportation relies on an odd phenomenon known as “quantum entanglement,” in which subatomic particles can become linked and influence each other instantaneously, regardless of how far apart they are. Scientists cannot distinguish the state of either particle until one is directly measured, but because the particles are connected, measuring one instantly determines the state of the other.

Currently, physicists can’t instantly transport matter (say, a human), but they can use quantum teleportation to beam information from one place to another. In a recent experiment, scientists at the National Institute of Standards and Technology (NIST) were able to teleport photons farther across an optical fiber than ever before.

“What’s exciting is that we were able to carry out quantum teleportation over such a long distance,” study co-author Martin Stevens, a quantum optics researcher at the NIST in Boulder, Colorado, told Live Science.

The new distance record was set using advanced single-photon detectors made of superconducting wires of molybdenum silicide that were about 150 nanometers (or billionths of a meter) wide and cooled to about minus 457 degrees Fahrenheit (minus 272 degrees Celsius), or about 1 degree above absolute zero. The experiment involved a near-infrared wavelength commonly used in telecommunications, the researchers said.

Quantum Teleportation Experiment
Colorized micrograph of one of the single-photon detectors made of superconducting nanowires patterned on MoSi used in the experiment.

“Only about 1 percent of photons make it all the way through 100 kilometers (60 miles) of fiber,” Stevens said in a statement. “We never could have done this experiment without these new detectors, which can measure this incredibly weak signal.”

The detectors used in this new experiment could record more than 80 percent of arriving photons, according to the scientists. In comparison, the previous record-holder had detectors that operated with about 75 percent efficiency at best. Moreover, the new experiment detected 10 times fewer stray photons than the previous record-holder.

Prior research did achieve quantum teleportation over longer distances over open air — a span of 89 miles (144 kilometers) between the two Canary Islands of La Palma and Tenerife, located off the northwest coast of Africa.

“However, the experiment at the Canary Islands involved a telescope on top of one mountain and a telescope on top of another mountain, with the telescopes pointed at each other at night, since background light during the day would interfere with the experiment,” Stevens said. “If you wanted quantum teleportation in the real world — say, from one city to another — you might not necessarily have a direct line-of-sight between two locations, and you wouldn’t want to be limited to working at night, so fiber optics might be more feasible.”

Quantum teleportation could enable the development of a “quantum Internet” that allows messages to be sent more securely, Stevens said.

“A quantum Internet could allow you to establish communications channels that are much more secure than what we have with the standard encryption protocols we use everyday nowadays,” Stevens said.

The researchers now plan to develop even better single-photon detectors to push distances for quantum teleportation even farther, Stevens said.

Quantum Teleportation Reaches Farthest Distance Yet

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A new distance record has been set in the strange world of quantum teleportation.
In a recent experiment, the quantum state (the direction it was spinning) of a light particle instantly traveled 15.5 miles (25 kilometers) across an optical fiber, becoming the farthest successful quantum teleportation feat yet. Advances in quantum teleportation could lead to better Internet and communication security, and get scientists closer to developing quantum computers.
About five years ago, researchers could only teleport quantum information, such as which direction a particle is spinning, across a few meters. Now, they can beam that information across several miles. [Twisted Physics: 7 Mind-Blowing Findings]

Quantum teleportation doesn’t mean it’s possible for a person to instantly pop from New York to London, or be instantly beamed aboard a spacecraft like in television’s “Star Trek.” Physicists can’t instantly transport matter, but they can instantly transport information through quantum teleportation. This works thanks to a bizarre quantum mechanics property called entanglement.
Quantum entanglement happens when two subatomic particles stay connected no matter how far apart they are. When one particle is disturbed, it instantly affects the entangled partner. It’s impossible to tell the state of either particle until one is directly measured, but measuring one particle instantly determines the state of its partner.
In the new, record-breaking experiment, researchers from the University of Geneva, NASA’s Jet Propulsion Laboratory and the National Institute of Standards and Technology used a superfast laser to pump out photons. Every once in a while, two photons would become entangled. Once the researchers had an entangled pair, they sent one down the optical fiber and stored the other in a crystal at the end of the cable. Then, the researchers shot a third particle of light at the photon traveling down the cable. When the two collided, they obliterated each other.
Though both photons vanished, the quantum information from the collision appeared in the crystal that held the second entangled photon.
Going the distance
Quantum information has already been transferred dozens of miles, but this is the farthest it’s been transported using an optical fiber, and then recorded and stored at the other end. Other quantum teleportation experiments that beamed photons farther used lasers instead of optical fibers to send the information. But unlike the laser method, the optical-fiber method could eventually be used to develop technology like quantum computers that are capable of extremely fast computing, or quantum cryptography that could make secure communication possible.
Physicists think quantum teleportation will lead to secure wireless communication — something that is extremely difficult but important in an increasingly digital world. Advances in quantum teleportation could also help make online banking more secure.