Qutrit...

Credit: Getty Images

Topics: Computer Engineering, Quantum Computing, Quantum Teleportation, Star Trek

For the first time, researchers have teleported a qutrit, a tripartite unit of quantum information. The independent results from two teams are an important advance for the field of quantum teleportation, which has long been limited to qubits—units of quantum information akin to the binary “bits” used in classical computing.

These proof-of-concept experiments demonstrate that qutrits, which can carry more information and have greater resistance to noise than qubits, may be used in future quantum networks.

Chinese physicist Guang-Can Guo and his colleagues at the University of Science and Technology of China (USTC) reported their results in a preprint paper on April 28, although that work remains to be published in a peer-reviewed journal. On June 24 the other team, an international collaboration headed by Anton Zeilinger of the Austrian Academy of Sciences and Jian-Wei Pan of USTC, reported its results in a preprint paper that has been accepted for publication in Physical Review Letters. That close timing—as well as the significance of the result—has each team vying for credit and making critiques of the other’s work.

The name quantum teleportation brings to mind a technology out of Star Trek, where “transporters” can “beam” macroscale objects—even living humans—between far-distant points in space. Reality is less glamorous. In quantum teleportation, the states of two entangled particles are what is transported—for instance, the spin of an electron. Even when far apart, entangled particles share a mysterious connection; in the case of two entangled electrons, whatever happens to one’s spin influences that of the other, instantaneously.

“Qutrit” Experiments Are a First in Quantum Teleportation, Daniel Garisto, Scientific American

7 Kilometers...

Calgary has seen quantum communication
brettA/Getty

Topics: Computer Science, Entanglement, Quantum Computer, Quantum Teleportation

A little math for perspective: 7 kilometers x 1,000 meters/1 kilometer x 39.37 inches/1 meter x 1 foot/12 inches x 1 mile/5,280 feet = 4.35 miles. Fiber optic cables typically have a range, and stations to repeat/boost the signals. This could be improved of course, and part of an infrastructure buildup that could spur the education industry K-12 and post secondary to prepare future workers for building a new communications architecture. A lot of automated and outsourced jobs are not coming back, and these likely wouldn't be frustrated by old money, like the fossil fuel industry does alternative energy.

A new world record for quantum teleportation has been set, bringing quantum communication networks that can stretch between cities a step closer. Two independent teams have transferred quantum information over several kilometres of fibre optic networks.

Being able to establish teleportation over long distances is a crucial step towards exchanging quantum cryptographic keys needed for encoding data sent over the fibres.

Quantum teleportation is a phenomenon in which the quantum states of one particle can be transferred to another, distant particle without anything physical traveling between them. It relies on a property called entanglement, in which measuring the state of one particle immediately affects the state of its entangled partner, regardless of the distance between them.

Conceptually, one way of doing teleportation involves three participants: say, Alice, Bob and Charlie. In order for Alice and Bob to exchange cryptographic keys, they have to first establish the capacity for teleportation, with Charlie’s help.

First Alice sends a particle (A) to Charlie. Bob, meanwhile, creates a pair of entangled particles (B & C), sends B to Charlie and holds on to C. Charlie receives both A and B, and measures the particles in such a way that it’s impossible to tell which particle was sent by Alice and which by Bob. This so-called Bell state measurement results in the quantum state of particle A being transferred to particle C, which is with Bob.

New Scientist:
Quantum teleportation over 7 kilometres of cables smashes record, Anil Ananthaswamy

Secure Quantum Teleportation...

Image Source: sakkmesterke/Shutterstock.com

Topics: Modern Physics, Quantum Computer, Quantum Mechanics, Quantum Teleportation

Although, "precise requirements" seems oxymoronic in a Heisenberg Uncertainty sense!

For the first time, researchers have demonstrated the precise requirements for secure quantum teleportation – and it involves a phenomenon known 'quantum steering', first proposed by Albert Einstein and Erwin Schrödinger.

Before you get too excited, no, this doesn't mean we can now teleport humans like they do on Star Trek (sorry). Instead, this research will allow people to use quantum entanglement to send information across large distances without anyone else being able to eavesdrop. Which is almost as cool, because this is how we'll form the un-hackable communication networks of the future.

Science Alert:
Scientists have figured out what we need to achieve secure quantum teleportation
Fiona MacDonald

1st Quantum Logic Operation...

Technology Review

TECHNOLOGY REVIEW: The first teleportation of a photon inside a photonic chip illustrates both the potential for quantum computation and the significant challenges that lay ahead.

Back in 2001, an obscure group of theoretical physicists proved a remarkable result. They showed that it was possible to build a quantum computer out of ordinary optical components, such as mirrors, lenses, lasers and so on.

That was something of a surprise. Until then, physicists had thought that quantum computing would only be possible using non-linear crystals and other exotic components that are hard to control.

The prospect of using ordinary bits and pieces has an important consequence. It immediately suggests that more powerful devices can be built simply by adding extra components. This problem of scalability has always plagued other attempts to build quantum computers.

The reaction from the theoretical physics community was barely controlled excitement. But in practice, this approach has never lived up to its early promise. That’s because it is hard to build even ordinary optical components into chip-like devices that can be scaled like conventional silicon chips. It is just not possible to manufacture them with the required performance and tolerances.

Today, Benjamin Metcalf at the University of Oxford and a few pals show how they are tackling these problems while aiming for the ultimate goal of scalable quantum computation. These guys have built the first self-contained photonic chip capable of teleportation, one of the fundamental logic operations necessary for quantum computation. The device is a proof-of-principle demonstration that scalable quantum computers of this type are firmly in the crosshairs of experimental physicists. But it also reveals that significant challenges lay ahead.

Physics arXiv: Quantum teleportation on a photonic chip
Benjamin J. Metcalf, Justin B. Spring, Peter C. Humphreys, Nicholas Thomas-peter, Marco Barbieri, W. Steven Kolthammer, Xian-min Jin, Nathan K. Langford, Dmytro Kundys, James C. Gates, Brian J. Smith, Peter G. R. Smith, Ian A. Walmsley

Quantum Physics and Grandfathers...

Entering a closed timelike curve tomorrow means you could end up at today.
Credit: Dmitry Schidlovsky

Applies works pretty well if your "grandfather" is a photon like yourself...

Closed timelike curves

The source of time travel speculation lies in the fact that our best physical theories seem to contain no prohibitions on traveling backward through time. The feat should be possible based on Einstein's theory of general relativity, which describes gravity as the warping of spacetime by energy and matter. An extremely powerful gravitational field, such as that produced by a spinning black hole, could in principle profoundly warp the fabric of existence so that spacetime bends back on itself. This would create a "closed timelike curve," or CTC, a loop that could be traversed to travel back in time.

Experimenting with a curve

Recently Ralph and his PhD student Martin Ringbauer led a team that experimentally simulated Deutsch's model of CTCs for the very first time, testing and confirming many aspects of the two-decades-old theory. Their findings are published in Nature Communications. Much of their simulation revolved around investigating how Deutsch's model deals with the “grandfather paradox,” a hypothetical scenario in which someone uses a CTC to travel back through time to murder her own grandfather, thus preventing her own later birth. (Scientific American is part of Nature Publishing Group.)

Deutsch's quantum solution to the grandfather paradox works something like this:

Instead of a human being traversing a CTC to kill her ancestor, imagine that a fundamental particle goes back in time to flip a switch on the particle-generating machine that created it. If the particle flips the switch, the machine emits a particle—the particle—back into the CTC; if the switch isn't flipped, the machine emits nothing. In this scenario there is no a priori deterministic certainty to the particle's emission, only a distribution of probabilities. Deutsch's insight was to postulate self-consistency in the quantum realm, to insist that any particle entering one end of a CTC must emerge at the other end with identical properties. Therefore, a particle emitted by the machine with a probability of one half would enter the CTC and come out the other end to flip the switch with a probability of one half, imbuing itself at birth with a probability of one half of going back to flip the switch. If the particle were a person, she would be born with a one-half probability of killing her grandfather, giving her grandfather a one-half probability of escaping death at her hands—good enough in probabilistic terms to close the causative loop and escape the paradox. Strange though it may be, this solution is in keeping with the known laws of quantum mechanics.

Scientific American: Time Travel Simulation Resolves “Grandfather Paradox”, Lee Billings

Diamond Teleportation...

The ability to teleport quantum information between diamond crystals that can also store it is a small but important step toward a quantum Internet.

TECHNOLOGY REVIEW: The prospect of a quantum Internet has excited physicists for two decades. A quantum Internet will allow the transmission of information around the world with perfect security and make cloud-based quantum computing a reality.

But first, physicists must perfect the technology of quantum routing—the ability to receive and transmit quantum information without destroying it.

That’s a significant challenge. The key is a technique called quantum teleportation, which transmits information from one point to another without it passing through the space in between. This is a routine operation in any decent quantum optics lab but quantum routing—which concatenates the process—is another challenge altogether.

Today, Wolfgang Pfaff at the Kavli Institute of Nanoscience Delft in the Netherlands and a few pals say they’ve take a significant step toward this goal with the first demonstration of diamond teleporters that can act as nodes in a quantum network. “These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-based quantum computing,” they say.

The fundamental difficulty in quantum routing is that quantum information is fragile stuff. So quantum teleportation has always involved creating a qubit, teleporting it and then immediately measuring it to check whether teleportation has been successful.

However, the process of measurement destroys quantum information. So an important goal is to create routers that can read and write quantum information without destroying it.

Physics arXiv:
Unconditional quantum teleportation between distant solid-state qubits

Physics' Top 10...

Source: AAAS (see #9)

1. Neutrino Mass
2. Shor's Algorithm
3. Accelerating universe
4. Extrasolar planets
5. Higgs Boson
6. Quantum Error Correction
7. Topological Insulators (TI)
8. AdS/CFT
9. Bose-Einstein Condensate
10. Quantum Teleportation

Neutrino Mass - surprisingly, neutrinos have a nonzero mass, which provides a window into particle physics beyond the standard model. THE STANDARD MODEL has been getting a lot of attention recently. This is well deserved in my opinion, considering that the vast majority of its predictions have come true, most of which were made by the end of the 1960s. Last year’s discovery of the Higgs Boson is the feather in its cap.

Shor's Algorithm - a quantum computer can factor N=1433301577 into 37811*37907 exponentially faster than a classical computer. This result from Peter Shor in 1994 is near and dear to our quantum hearts. It opened the floodgates showing that there are tasks a quantum computer could perform exponentially faster than a classical computer.

Accelerating universe - the universe is expanding, and the rate of this expansion is increasing. This result has been the source of an incredible number of misconceptions. First, how do we know this is happening? In the 1920s astronomers discovered that some of the really faint ‘stars’ that we see in the night sky are actually distant galaxies. Shortly thereafter, it was discovered that these galaxies are actually moving away from us, and away from each other. The question becomes: how did this happen?

Extrasolar planets - over the past two decades, we have detected ~1000 planets outside of our own solar system. As a prerequisite for finding extrasolar life–unless they find us first–we need to discover candidate homes.

Higgs Boson - The Higgs “field” permeates all of space; excitations in this field are interpreted as particles (Higgs bosons); these particles give other particles mass.

Quantum Error Correction - we want to protect quantum information from noise. We also face this challenge with classical computers. It also turns out that our enemy is formidable: we are battling decoherence. One way to think about decoherence is that every quantum system interacts with its environment, creating entanglement between the two – since we can’t control the environment (it both large and unknown), we lost control of our quantum system.

Topological Insulators (TI) - we’ve known for a long time that solids, liquids, gases and plasmas aren’t the only phases of matter; but only recently, we’ve unexpectedly discovered a huge new class of phases. Before topological phases, we classified phases based upon their local symmetries. In the early 1980s, experimentalists discovered quantum hall systems, which were the first materials whose ground states couldn’t be differentiated by only using a local description. The ‘phases of matter can’ had a few dents in it, but the lid was blown sky-high when topological Insulators were discovered in 2006. These materials have bizarre properties; they provide the foundation for a multitude of cousin systems; they are shedding light on questions from fundamental physics; and they will probably be widely utilized in the electronics of the 21st century.

AdS/CFT - AdS/CFT, which sometimes gets called the holographic principle, is basically a mathematical toolkit which says that in certain situations, there is an exact correspondence between gravity problems in n+1-dimensions and strongly correlated electron systems in n-dimensions.

Bose-Einstein Condensate - One of the original BEC experiments involved cooling thousands of Rubidium atoms to extremely low temperatures (a few nanokelvin above absolute zero), at which point their behavior is described by quantum mechanics. The Rubidium atoms behave as predicted, where the thousands of atoms coalesce into a very small area.

Quantum Teleportation - Why is this amazing? Well, teleportation would certainly be amazing, but that’s a bit of a misnomer, and a point I tried to clarify in my posts. Quantum teleportation IS NOT an all-purpose teleportation protocol. But it is incredibly awesome, and will undoubtedly have major technological significance someday. Basically, it’s easy to send photons all over the universe (we are very good at building and operating lasers), but it’s very hard to send more exotic forms of matter, especially when the matter is supposed to stay in a specific quantum state. Quantum teleportation allows us to first spread entangled matter throughout space. Then, at a later time, we can exploit this resource to move delicate quantum states to the location of our entangled matter.

Quantum Frontiers:
The 10 biggest breakthroughs in physics over the past 25 years according to us

Quantum Remote Control...

...and, physicists know how to do it! ~!!!~

TECHNOLOGY REVIEW: Teleportation is one of the more extraordinary phenomena in the quantum world. It allows a quantum object, such as a photon or electron, to travel from one location to another without passing through the space in between.

Teleportation is a standard procedure in any decent quantum mechanics laboratory. Physicists use it on a daily basis for quantum communication and quantum computation.

If that sounds exotic, you ain’t seen nothing yet; teleportation is about to get a whole lot weirder. That’s because until now, physicists have only been able to teleport single particles, one at a time. Today, Christine Muschik at the Mediterranean Technology Park in Barcelona and a bunch of mates say they’ve worked out how to teleport quantum stuff continuously.

That will allow them to manipulate one quantum particle while watching the effects occur in another particle elsewhere. That’s essentially quantum remote control.

Physics arXiv:
Quantum Teleportation of Dynamics and Effective Interations between Remote Systems

In Trek Retropect...

Memory-built-in quantum teleportation between photonic and atomic qubits

I could have easily discussed the anniversary of 9-11, my recollection of the celebrations that broke out spontaneously last year (my neighbors made it quite hard to sleep); my shear luck of being in New York as those infectious celebrations happened.

No...instead I'm in a Trekkie mood, looking forward to the future; hopeful. We started the 21^st Century on a sour note to say the least.

From the 100 Year Starship Symposium in Houston I blogged on yesterday, I stumbled on this item. The paper is at the link below. It took me aback that the Air Force commissioned the research, but I guess you have to study these things...even if we ultimately can't, what will we learn from the effort?

Lest you think that our friends at DARPA are the only ones interested in science-fictional possibilities, the USAF recently took delivery of a new study regarding the military potential of teleportation.

The Teleportation Physics Study was done by Eric Davis of Warp Drive Metrics. Its purpose -

"This study was tasked with the purpose of collecting information describing the teleportation of material objects, providing a description of teleportation as it occurs in physics, its theoretical and experimental status, and a projection of potential applications. The study also consisted of a search for teleportation phenomena occurring naturally or under laboratory conditions that can be assembled into a model describing the conditions required to accomplish the transfer of objects."

Federation of American Scientists: Teleporation Physics Study