Quantum Research

Quantum Internet, Quantum Research

Quantum Teleportation: Paving the Way for a Quantum Internet


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Last week’s big quantum news centred on two proof of concept studies, both of which claim to have achieved quantum teleportation using a tripartite unit of quantum information called a qutrit, for the first time. While quantum teleportation has been demonstrated previously, it has only been carried out with qubits, which are capable of storing less information than qutrits but thought to be more stable. The novel feat was achieved independently by two teams, one led by Chinese physicist Guang-Can Guo at the University of Science and Technology of China (USTC) and the other, an international collaboration headed by Anton Zeilinger of the Austrian Academy of Sciences and Jian-Wei Pan of USTC. While both teams have reported their results in preprint articles, the article by the Austrian-led team has been accepted for publication in Physical Review Letters.

Competition for credit of this achievement aside, the team’s findings ultimately support each other in substantiating an advancement in quantum teleportation theory: namely, that quantum networks should be capable of carrying far more information with less interference than previously thought. This advancement—like many in the world of quantum—is likely to be found most exciting for physicists, evading the grasp of an applied significance for those of us with less scientific minds. Nevertheless, the notion of quantum teleportation has once again grabbed headlines and imaginations, providing a good opportunity to explore the concept and the applied significance that advancements like this might eventually have on our world.

While it may sound flash, quantum teleportation is an affair less akin to science fiction than one might imagine. On a basic level, quantum teleportation differs from ‘Star Trek teleportation’ because it is used to transmit information rather than macroscale physical objects, like human beings. This is possible because of quantum entanglement, a phenomenon of quantum physics that allows us to look at one particle or group of particles and know things about another, even if those particles are separated by vast distances. Quantum teleportation relies on entanglement to transfer information based on this shared state of being demonstrated by entangled particles. As such, quantum teleportation can be defined as “the instantaneous transfer of a state between particles separated by a long distance”.

Quantum teleportation holds the most obvious promise in the discipline of quantum communication, where its impact in secure communication was established as early as 1997. In 2017, Chinese scientists working with a team in Austria made waves with their announcement that they had achieved transnational quantum teleportation, establishing a quantum-secure connection for a video conference between the Chinese Academy of Sciences in Beijing and the Austrian Academy of Sciences in Vienna, some 7,600 kilometres away from each other. The experiment utilized China’s Micius satellite to transmit information securely using photons. Micius is a highly sensitive photon receiver, capable of detecting the quantum states of single photons fired from the ground. These photons, beamed via Micius, acted as qubits, allowing researchers in both countries to access a shared quantum key and thus enabling them to participate in the quantum-encrypted video call. Critically, should the data have been accessed by a third party, the code would be scrambled, leaving evidence of tampering for researchers at both ends of the connection.

This experiment, facilitated by quantum teleportation, proved two fundamental and impactful theories in quantum physics: that quantum communication can provide a previously unfathomable level of security and that it is capable of doing so on a global scale. Given these capabilities and coupled with the new qutrit proof-of-concept work, the realm of applied possibilities for quantum teleportation is expanding.

Aside from ultra-secure, transcontinental video conferences, one very hyped application for quantum teleportation is in the development of a hyper-fast quantum internet. Due to the entangled state of particles, information is transmitted instantaneously in quantum teleportation—faster than the speed of light. However, the transfer of this information is still required to operate within the current confines of classical communication. As such, even quantum information must travel through ground-based fibre optic cables or via photon-sensitive space-based satellites, like China’s Micius. This infrastructure is both expensive and potentially expansive, posing a formidable challenge for a global roll-out of a quantum internet. Still, these early experiments have laid the groundwork for the development of a quantum-secure Wi-Fi by putting theory to the test and producing promising results.

Currently, a team of researchers at Delft University in the Netherlands is working to build a quantum network, using quantum teleportation as the mode of transport for information between linkage points. The project, which aims to connect four cities in the Netherlands, is scheduled for completion in 2020. In China too, researchers are constructing the backbone for a quantum network to connect Beijing and Shanghai. Aside from the support of private corporations such as banks and other commercial entities, progress on the concept of both localised and international quantum networks has been spurned by pressing anxiety about global levels of cybersecurity

A critical advantage to a future quantum internet is the enhanced security afforded by quantum teleportation—the ability to create an unhackable connection. This could have serious implications for national security and could present a potential solution for many foreign surveillance and interference challenges that countries face today. For example, it is now public knowledge in the U.S. that Russia has the demonstrative ability to directly interfere with most paperless voting systems. While states are currently reticent about making changes to the current U.S. vote-casting system, alternatives are slowly being considered—from regressive paper ballot casting to progressive blockchain applications—in order to safeguard American votes against hacking efforts. Quantum teleportation could offer an interesting alternative in this space as the technology continues to develop.

Though quantum teleportation will not be transporting human beings between planets any time soon, it will play a key role in ushering in an internet revolution. While it remains to be seen exactly how that revolution will play out, it is clear that it will bring an unprecedented level of security and speed to global communications. It is also apparent that the level of interest in the secure and high-speed communications afforded through quantum teleportation is broad and deep, spanning both public and private sectors across the globe. Quantum teleportation has recently seen a number of experimental proofs, pushing the field of quantum communications to the fore of quantum development and promising to deliver a much sought-after security transformation within the decade.

Quantum Computing, Quantum Research

Saving Schrödinger’s Cat: Researchers Discover an Early Warning Signal for Quantum Jumps


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Feature image via Science X.

Gabriella Skoff

Schrödinger’s cat is a thought experiment that has become well known as a symbol for the “weirdness” and unpredictability of the phenomenon of quantum superposition. The eponymous thought experiment devised by Austrian physicist Erwin Schrödinger in 1935 involves a cat, a vial of poison, a radioactive substance and a sealed box. The experiment dictates that if an atom of the radioactive substance decays then it will trigger the release of the poison, killing the cat; however, that may or may not happen. One can only find out if this has occurred, and therefore if the cat is alive or dead, by opening the box to observe the state of being of the cat. According to the Copenhagen Interpretation of quantum physics, until the observer peeks inside the box, the cat is actually both dead and alive. It is only when the state of the cat is observed, therefore, that the quantum superposition collapses into one or the other states and the cat is found to be either dead or alive.

Based on Niels Bohr’s 1913 proposal of quantum jumps, it was thought that the process of the cat collapsing into a theoretically dead or alive state upon observation was both instantaneous and unpredictable. However, new experimental research performed by a team of Yale researchers and published last week in Nature journal, suggests otherwise. Dr Zlatko Minev and his team’s findings conclude that a quantum jump does not actually exhibit the random, abruptness that defines the fate of Schrödinger’s cat. Rather, their research suggests, “the evolution of each [quantum] jump is continuous, coherent and deterministic”.

Within the context of Schrödinger’s cat paradox, these findings imply that the continued-life/death of the cat is simply the final stage of a process rather than an instant occurrence without foreshadowing. Further, the Yale team has detected “an advance warning signal” which indicates that a jump is about to occur. This seems to signify that we can not only detect when a quantum jump will occur but that we can also potentially reverse it during the transition. These new findings not only impact our theoretical ability to potentially save Schrödinger’s cat from its proverbial death but also have a fundamental impact in applied quantum computing.

The conundrum of a quantum jump has long presented a challenge in the applied field of quantum computing, where a jump in qubits manifest as an error in calculations. Researchers are hopeful that these new findings could potentially facilitate major advances in understanding and controlling quantum information. They anticipate that this new discovery will help to develop an early warning system that can predict when a jump, and therefore a computational error, is about to occur in order to catch it before it happens and reverse its course. While it would be a wonderful conclusion that Schrödinger’s dear cat could be saved, the real value of this research lies in its applied context: the potential to develop an advanced monitoring, detection and correction function for quantum systems, which could help bring us one step closer to a quantum advantage.

 

 

Quantum Research

The Quantum Question of an Objective Reality


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Rick and Morty explore the multiverse, a spin on the Many Worlds Interpretation.
Image via Adult Swim

Gabriella Skoff

Thought experiments in the domain of quantum physics have long captured the public imagination with their strange and “spooky” nature. Schrödinger’s at once dead-and-alive cat and its lesser-known extension, Eugene Wigner’s eponymous Wigner’s Friend, are two famous thought experiments which examine the concept of superposition and the role of the observer in quantum interactions. Until very recently, quantum technologies were simply not advanced enough to replicate Wigner’s Friend and an experiment modelled on Schrödinger’s Cat would no doubt raise serious ethical concerns for animal rights. As such, since their inception these thought experiments have been relegated to the realm of theory and imagination.

That changed last week, when Massimiliano Proietti and his team at Heriot-Watt University in Edinburgh succeeded in performing an experiment modelled on the Wigner’s friend scenario in a laboratory setting. Through this experiment, the researchers sought to explore what is known as the measurement problem—the question of how, and if, the wave function collapse occurs—the central problem in quantum mechanical interpretations.

Using the groundwork previously laid by researchers from the University of Vienna in Austria, the Edinburgh team carried out an extension of the Wigner’s Friend scenario using a “state-of-the-art 6 photon experiment”. The researchers used six entangled photons to simulate a scenario in which the role of both Wigner and his friend were occupied by measuring equipment instead of scientists. As in the thought experiment: “Wigner’s friend measures the polarization of a photon and stores the result. Wigner then performs an interference measurement to determine if the measurement and the photon are in a superposition.”

The experimental setup, as depicted by the researchers. image via
arxiv.org/abs/1902.05080 

The as yet unpublished results prove Wigner’s theory correct. The researcher’s findings suggest that two observers of a quantum interaction can observe two different realities, which are both equally real and correct simultaneously, even if they contradict each other. The implication of this assertion is that in quantum physics there is no objective reality; that reality itself is observer-dependent. The authors of the study suggest that these results necessitate an evolution in our understanding of quantum theory, a shift toward theoretical frameworks that are observer-dependent and away from interpretations that are not.

The impact of this conclusion, which proposes an unconventional interpretation of the notion of reality, could extend far beyond the discipline of physics.

Strikingly, the assumption that multiple, contradictory realities can coexist calls the concept of objective fact—the very pursuit of science itself—into question. This point, posed in an article by the MIT Tech Review, jeopardizes the assumption of the existence of “universal facts”. How might an understanding of the world around us, in which there is no shared, objective reality, change not just science but also social theory?

Of course, it is hasty to argue that quantum theory applies seamlessly to the social world, suggesting there is a direct, logical mapping. Thus far, the topic of how the microscopic quantum world effects our macroscopic, visible world has not been fully explored through research. That does not mean, however, that there is no symmetry. The question of the universality of quantum theory continues to permeate thinking today, much as it had captured the imagination of quantum theorists in the early 1900’s.

Schrödinger’s Cat (1935), for example, explores the question of the relationship between quantum and classical reality. Among other revelations, this thought experiment suggests that projecting nanoscale quantum theory onto a macro-scale experiment produces logic-defying results, ultimately leading to the conclusion that a cat cannot be both alive and dead at the same time. Schrödinger wished to argue that the dominant Copenhagen Interpretation of quantum physics, which states that an object in a state of quantum superimposition can exist in all possible configurations, does not hold at the macroscale.

Nevertheless, this problem posed by the Copenhagen Interpretation, considered by Schrödinger to be settled by his theoretical experiment, persists.

The findings of the Edinburgh team suggest that in fact Schrödinger’s cat can be both dead and alive at the same time, leading to a whole new set of questions and theories. One way to accommodate for the experiment’s result, the authors write: “…is by proclaiming that “facts of the world” can only be established by a privileged observer—e.g., one that would have access to the “global wavefunction” in the many worlds interpretation or Bohmian mechanics.”

As the authors suggest, this research potentially validates the Many-Worlds Interpretation (MWI). The MWI, as the name suggests, stipulates that each quantum interaction produces not just one result but all possible results, which exist simultaneous, branching off to form different versions of reality and producing many independent histories, futures and worlds. The researchers propose that in order for the concept of objective reality to function in the context of their findings, the holder of that knowledge must, in a godlike fashion, have access to all information from every possible reality.

Scientific theory produces claims at knowing and understanding the world around us as it really is. Quantum physics, however, has the potential to unravel this by posing the most fundamental question of all: What is reality?