Discoveries in Quantum Teleportation Could Lead to Fault-Tolerant Computers and, Possibly, Wormholes

 

By James Myers and Mariana Meneses

Teleportation is fundamental to the operation of the quantum, which is the tiniest bit of energy in the universe that can either cause change or be changed.

Researchers are devising novel processes that could use the phenomenon of quantum teleportation to reduce error rates in today’s prototypes of the quantum computer and deliver a far more powerful machine in the near future.

Quantum teleportation is a process by which the state of a quantum particle is transferred from one location to another without physically moving the particle itself. This phenomenon exploits the principles of quantum entanglement, in which two quanta can connect such that they are both in the same state in spite of differences in time and space between them.

The word “teleportation” might bring to mind the science fiction series Star Trek, in which starship crew are rapidly transported through space by disassembling and reassembling the atoms in their bodies, but quantum teleportation isn’t that exotic or far-fetched, at least for now. Although quantum teleportation doesn’t move atoms through space, there are some similarities in that information can be transmitted from one place in space and time to another by copying a quantum state. 

 

 

Recently, scientists in China along with collaborators in Finland have demonstrated proof in principle of a new method to achieve high-fidelity quantum teleportation, even in noisy environments. By using a hybrid entanglement technique, they were able to overcome environmental noise and successfully teleport quantum states with nearly 90% accuracy. 

This breakthrough could greatly improve secure quantum communication by making quantum teleportation more reliable and efficient despite environmental interference that is otherwise difficult and costly to eliminate in the current generation of quantum computers. 

Today’s quantum computers, often referred to as noisy intermediate-scale quantum (NISQ) devices, are highly susceptible to errors which severely limit their computational capabilities and reliability. These errors arise from various sources, including imperfect quantum gates and environmental interference from heat and electromagnetism. Noise causes qubits, which are the information bits in the quantum computer, to disconnect. 

 

 

As a result of these frequent disconnections, called decoherence, NISQ devices can only perform relatively simple computations. At present, they are inadequate for solving complex, large-scale problems that quantum computers are theoretically capable of tackling with far greater power than today’s devices, such as factoring prime numbers, simulating complex molecules, and optimizing large systems.

Professor Jyrki Piilo, from the University of Turku in Finland, and Chuan-Feng Li, a professor at the University of Science and Technology of China in Hefei, have conducted experiments that predict a near-perfect means of achieving quantum teleportation that is actually enhanced by noise. They accomplished this by using noise to measure both the polarization of photons, which are particles of light whose states are most frequently used to measure quantum entanglement, and the frequency of the photons. 

In their experiments, two measurements rather than one enhanced the ability to achieve teleportation and transfer information between entangled quanta.

“When we have hybrid entanglement and add noise, the teleportation and quantum state transfer occur in almost perfect manner”, said Dr Olli Siltanen, whose doctoral dissertation presented the theoretical aspects of the research.

How would quantum teleportation work in quantum communications?

Dr. John Preskill is a leading expert on quantum teleportation and recently spoke about the process with astrophysicist Janna Lavin in Quanta Magazine’s Joy of Why podcast. Dr. Preskill is Professor of Theoretical Physics at the California Institute of Technology, founder and current leadership chair of the Institute for Quantum Information and Matter, and lead at Caltech’s new Center for Quantum Precision Measurement.

His recent publications have explored topics ranging from enhancing error resilience in quantum systems, such as the surface code’s response to error bursts and efficient soft-output decoders, to fundamental quantum limits in stochastic waveform estimation, to universal scaling laws in many-body quantum systems, among many others.

Preskill explains that for quantum teleportation of information to occur, initially two parties share a pair of entangled qubits, each party holding one of the pair. When a third qubit, whose state is unknown and needs to be teleported, interacts with the entangled qubit at the sender’s location through a special kind of joint measurement, it collapses into a new state that is correlated with the state of the entangled qubit pair. 

In the podcast, Preskill explains that the sender then communicates the result of this measurement to the receiver via classical means, for example by transmitting photons through an optical fiber. Using this information, the receiver can perform a specific operation on their entangled qubit, transforming it into an exact replica of the state of the third qubit. Consequently, the original qubit’s state has been effectively transferred to the receiver’s location, completing the teleportation process. 

This procedure preserves quantum information precisely, making it a crucial concept for advancements in quantum communication and quantum computing by avoiding the observer effect.

Measuring a quantum state is a tricky business because of the still-mysterious observer effect. As Dr. Preskill notes, “The mystery is this: You can’t observe a qubit without disturbing it. This is a very important difference between ordinary information and quantum information.” 

 

In our May feature The Observer Effect: Why Do Our Measurements Change Quantum Outcomes?, we discussed how the act of observation by conscious beings can influence the behavior of quantum particles, a phenomenon first demonstrated by Thomas Young’s double-slit experiment in 1801. This observer effect suggests that the very act of measuring or observing a quantum system causes interference and alters its behavior, challenging our classical understanding of reality as independent of observation. 

Will the future of quantum teleportation lead us to wormholes in spacetime?

Dr. Preskill discusses the possible consequences of teleportation and the greater accuracy in measurement that might one day result. 

“In the case of quantum computing, the best idea we currently have — and it’s an old idea, which goes back over 40 years to Richard Feynman — is that we can use quantum computers to understand more deeply how quantum systems behave. Physicists like us understand that that’s interesting, but it’s also important because it can enable the discovery of new types of materials with useful properties, new types of chemical compounds, perhaps including pharmaceuticals and so on. And all that eventually does affect people’s everyday lives. And with quantum measurement as well, I think quantum technology is really going to touch everything in science eventually.”

Preskill notes that he is especially interested in the ways that accurate quantum measurements could advance our understanding of black holes, the mysterious objects with massive gravitation where spacetime ends in the middle of practically every galaxy in the universe including our Milky Way. Precision measurements could also help to bring to life the theory of wormholes as conduits between black holes sharing an interior that was predicted in 1935 by Albert Einstein and collaborator Nathan Rosen, consistent with the equations of General Relativity.

Neil deGrasse Tyson and Brian Greene Confront the Edge of our Understanding: “Are entangled particles actually wormholes?”

 

Einstein and Rosen further collaborated with Boris Podolsky on a paper that describes, as Preskill states, the peculiar way in which quantum entanglement “allows systems to be correlated with one another in a way that we can’t describe in terms of classical information.”

As Preskill explained to Janna Levin, “These two phenomena, quantum entanglement and wormholes in space, are closely related to one another. In fact, they can be viewed as two ways of describing the same thing. This is a common thing in physics and very empowering. If we have two different ways to describe the same phenomenon, which look very different from one another, but describe exactly the same physics, that can empower us to get a deeper understanding.”

 

 

Preskill explained that the wormhole joining two black holes predicted by Einstein and Rosen would not be traversable for an object in spacetime like a qubit or a living being. However, science is now providing evidence that wormholes could be traversable. This could be accomplished by sending a negative energy pulse into a black hole causing its event horizon, or boundary, to project into the structure in a way that a qubit could be injected into one end and emerge at the other end of a wormhole.

Entanglement between the tiniest quanta and the largest structures like black holes arises from interactions between particles and is preserved even when the particles are separated. It defies classical intuitions of locality and realism, as illustrated by Einstein’s term “spooky action at a distance.” 

Preskill stated that “Einstein felt very strongly that there should be no randomness in the fundamental laws of physics. He felt that if we know everything that can be known — that the laws of physics will allow us to know — about a physical system, then we should be able to perfectly predict what we’ll see when we observe that system. And entanglement does not obey that principle. There really is true randomness in the world. Even if we know everything about that entangled pair of qubits that you and I share, still you are powerless to predict what you see when you look at that qubit. It’s just a random bit. And it’s not because you don’t know. It’s that it cannot be known.”

In the near-term, it seems probable that discoveries in quantum teleportation will help avoid the need for quantum error correction by providing a practical mechanism for transferring quantum states between particles without physically moving them.

When quantum teleportation is mastered, the resulting speed and accuracy of a fully functional quantum computer might one day give us the power to analyze the quantum basis of the largest structures in the universe such as black holes, and find a pathway that connects the massive objects and their gravity that sit in the middle of spacetime in our galaxy and practically every other.

When, and if, such a time will come to pass is unknowable, but we can trust that human ingenuity and the knowledge of researchers now collaborating on resolving the many questions will contribute in no small measure to a very intriguing future.

Craving more information? Check out these recommended TQR articles: 

• Race for Post-Quantum Cryptography: Will Proposed Encryption Standards Secure the World’s Data?
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• Breakthrough in Error Correction Opens Potential for Large-Scale Quantum Computer Processing
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