Could quantum physics unlock teleportation?

Date:
Thu, 20 Oct 2022 15:30:00 +0000

Description:
The article 'Teleportation: Beam Me Up, Bob' appeared in the November 1993 issue of Popular Science. Popular Science Physicists are making leaps in quantum teleportation, but it's still a long ways from 'Star Trek.' The post Could quantum physics unlock teleportation? appeared first on Popular Science .

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The article 'Teleportation: Beam Me Up, Bob' appeared in the November 1993 issue of Popular Science. Popular Science

From cities in the sky to robot butlers, futuristic visions fill the history of PopSci . In the Are we there yet? column we check in on progress towards our most ambitious promises. Read the series and explore all our 150th anniversary coverage here . Jetpacks , flying cars , hoverboards , bullet trains inventors have dreamt up all kinds of creative ways, from science fiction to science fact, to get from point A to point B. But when it comes to transportation nirvana, nothing beats teleportationvehicle-free,
instantaneous travel. Ifbeam-me-up-Scotty technology has gotten less
attention than other transportation tropes Popular Science ran short explainers in November 1993 and September 2004 its not because the idea isnt appealing. Regrettably, over the decades there just hasnt been much progress in teleportation science to report. However, since the 2010s, new discoveries on the subatomic level are shaking up the playing field: specifically,
quantum teleportation.

Just this month, the 2022 Nobel Prize in Physics was awarded to three scientists for experiments with entangled photons, according to the Royal Swedish Academy of Sciences , which selects the winners. The recipients work demonstrated that teleportation is possiblewell, at least between photons
(and with some serious caveats on what could be teleported). The physicists Alain Aspect , John Clauser , and Anton Zeilinger had independent breakthroughs over the last several decades . The result of their work not only demonstrated quantum entanglement in action but also showed how the arcane property could be a channel to teleport quantum information from one photon to another. While their findings are not anywhere close to
transforming airports and train stations into Star Trek -style transporters, they have been making their way into promising applications, including
quantum computing, quantum networks, and quantum encryption .

Teleportation is a very inspiring word, says Maria Spiropulu, the Shang-Yi Chen professor of physics at the California Institute of Technology , and director of the INQNET quantum network program. It evokes our senses and suggests that a weird phenomenon is taking place. But nothing weird is taking place in quantum teleportation.

When quantum mechanics was being hashed out in the early 20th century between physicists like Max Planck , Albert Einstein , Niels Bohr , and Erwin Schrdinger , it was becoming clear that at the subatomic particle level, nature appeared to have its own hidden communication channel, called quantum entanglement. Einstein described the phenomenon scientifically in a paper published in 1935 , but famously called it spooky action at a distance
because it appeared to defy the normal rules of physics. At the time, it seemed as fantastical as teleportation, a phrase first coined by writer Charles Fort just four years earlier to describe unexplainable spectacles
like UFOs and poltergeists.

Fifty years ago, when scientists started doing [quantum] experiments, says Spiropulu, it was still considered quite esoteric. As if in tribute to those scientists, Spiropulu has a print honoring physicist Richard Feynman in her office. Feynman won the Nobel Prize in 1965 for his Feynman diagrams, a graphical interpretation of quantum mechanics.

Spiropulu equates quantum entanglement with shared memories. Once you marry, it doesnt matter how many divorces you may have, she explains. Because youve made memories together, you are connected forever. At a subatomic level, the shared memories between particles enables instantaneous transfer of information about quantum stateslike atomic spin and photon polarizationbetween distant particles. These bits of information are called quantum bits, or qubits . Classical digital bits are binary, meaning that
they can only hold the value of 1 or 0, but qubits can represent any range between 0 and 1 in a superposition, meaning theres a certain probability of being 0 and certain probability of being 1 at the same time. Qubits ability
to take on an infinite number of potential values simultaneously allows them to process information much fasterand thats just what physicists are looking for in a system that leverages quantum teleportation.

[Related: Quantum teleportation is real, but its not what you think ]

But for qubits to work as information processors, they need to share information the way classical computer chips share information. Enter entanglement and teleportation. By entangling subatomic particles, like photons or electronsthe qubitsand then separating them, operations can be performed on one that generates an instantaneous response in its entangled twin.

The farthest distance to date that qubits have been separated was set by Chinese scientists , who used quantum entanglement to send information from Tibet to a satellite in orbit 870 miles away. On terra firma, the record is just tens of miles , traveling through fiber optic connections and through
air (line of sight lasers).

Qubits strange behavioracting like theyre still together no matter how far apart theyve been separatedcontinues to puzzle but amaze physicists. It does appear magical, Spiropulu admits. The effect appears very, wow! But once you break it down, then its engineering. And in just the past five years, great strides have been made in quantum engineering to apply the mysterious but predictable characteristics of qubits. Besides quantum computing advances
made by tech giants like Google , IBM , and Microsoft , Spiropulu has been spearheading a government- and privately funded program to build out a
quantum internet that leverages quantum teleportation.
With some guidance from Spiropulus postdoctoral researchers at Caltech, Venkata R. (Raju) Valivarthi and Neil Sinclair , this is how state-of-the-art quantum teleportation would work (you might want to strap yourself in): Step 1: Entangle

Using a laser, a stream of photons shoots through a special optical crystal that can split photons into pairs. The pair of photons are now entangled, meaning they share information. When one changes, the other will, too. Step
2: Open a quantum teleportation channel

Then, one of the two photons is sent over a fiber optic cable (or another medium capable of transmitting light, such as air or space) to a distant location.This opens a quantum channel for teleportation. The distant photon (labeled photon one above) becomes the receiver, while the photon that
remains behind (labeled photon two) is the transmitter. This channel does not necessarily indicate the direction of information flow as the photons could
be distributed in roundabout ways. Step 3: Prepare a message for
teleportation

A third photon is added to the mix, and is encoded with the information to be teleported. This third photon is the message carrier. The types of
information transmittedcouldbe encoded into whats called the photons properties, or state, such as its position, polarization, and momenta. (This is where qubits come in, if you think of the encoded message in terms of 0s, 1s, and their superpositions.) Step 4: Teleport the encoded message

One of the curious properties of quantum physics is that a particles state,
or properties, such as its spin or position, cannot be known until it is measured. You can think of it like dice. A single die can hold up to six values, but its value isnt known until its rolled. Measuring a particle is like rolling dice, it locks in a specific value. In teleportation, once the third photon is encoded, a joint measurement is taken of the second and third photons properties, which means their states are measured at the same time
and their values are locked in (like viewing the value of a pair of dice).
The act of measuring changes the state of the second photon to match the
state of the third photon. As soon as the second photon changes, the first photon, on the receiving end of the quantum channel, snaps into a matching state.

Now the information lies with photon onethe receiver. However, even though
the information has been teleported to the distant location, its still encoded, which means that like an unrolled die its indeterminate until it can be decoded, or measured. The measurement of photon one needs to match the joint measurement taken on photons two and three. So the outcome of the joint measurement taken on photons two and three is recorded and sent to photon
ones location so it can be repeated to unlock the information. At this point, photons two and three are gone because the act of measuring photons destroys them. Photons are absorbed by whatever is used to measure them, like our
eyes. Step 5: Complete the teleportation

To decode the state of photon one and complete the teleportation, photon one must be manipulated based on the outcome of the joint measurement, also
called rotating it, which is like rolling the dice the same way they were rolled before for photons one and two. This decodes the messagesimilar to how binary 1s and 0s are translated into text or numeric values. The
teleportation may seem instantaneous on the surface, but because the decoding instructions from the joint measurement can only be sent using light (in this scenario over a fiber optic cable), the photons only transfer the information at the speed of light. Thats important because teleportation would otherwise violate Einsteins relativity principle, which states that nothing travels faster than the speed of lightif it did, this would lead to all sorts of bizarre implications and possibly upend physics. Now, the encoded information in photon three (the messenger) has been teleported from photon twos position (transmitter) to photon ones position (receiver) and decoded.

Whew! Quantum teleportation complete.

Since we transmit digital bits today using light, it might seem like quantum teleportation and quantum networks offer no inherent advantage. But the difference is significant. Qubits can convey much more information than bits. Plus, quantum networks are more secure, since attempts to interfere with quantum entanglement would destroy the open quantum channel.

Researchers have discovered many different ways to entangle, transmit, and measure subatomic information. Plus, theyre upgrading from teleporting information about photons, to teleporting information about larger-sized particles like electrons , and even atoms .

[Related: Warp speed space travel just got a tiny bit more realistic ]

But its still just information being transmitted, not matterthe stuff that humans are made of. While the ultimate dream may be human teleportation, it actually might be a good thing were not there yet.

The Star Trek television and film franchise not only helped popularize teleportation but also glamorized it with a glittery dissolve effect and catchy transporter-tone. The Fly , on the other hand, a movie about teleportation gone wrong, painted a much darker, but possibly scientifically truer picture of teleportation. Thats because teleportation is really an act of reincarnation. Teleportation of living matter is risky business: It would require scanning the travelers information at the point of departure, transmitting that information to the desired coordinates, and deconstructing them at the point of departure while simultaneously reconstructing the traveler at the point of arrivalwe wouldnt want errant copies of ourselves on the loose. Nor would we want to arrive as a lifeless copy of ourselves. We would have to arrive with all our beating, breathing, blinking systems intact in order for the process to be a success. Teleporting living beings, at its core, is a matter of life and death.

Or not.

Formidable minds, such as Stephen Hawking, have proposed that the
information, or vector state, that is teleported over quantum entanglement channels does not have to be confined to subatomic particle properties. In fact, entire blackholes worth of trapped information could be teleported, according to this theory. It gets weird, but by entangling two blackholes and connecting them with a wormhole (a space-time shortcut), information that disappears into one blackhole might emerge from the other as a hologram.
Under this reasoning, the vector states of molecules, humans, and even entire planets could theoretically be teleported as holograms.

Kip Thorne , a Caltech physicist who won the 2017 Nobel Prize in Physics for gravity wave detection, may have best explained the possibilities of teleportation and time travel as far back as 1988 : One can imagine an advanced civilization pulling a wormhole out of the quantum foam and
enlarging it to classical size. This might be analyzed by techniques now
being developed for computation of spontaneous wormhole production by quantum tunneling.

For now, Spiropulu remains focused on the immediate promise of quantum teleportation. But it wont look anything like Star Trek. Beam me up, Scotty? No such things, she says. But yes, a lot of progress. And its transformative.

The post Could quantum physics unlock teleportation? appeared first on
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