Quantum Quandaries

by Heath Miller
December 8th 2012

What if you could transfer a file faster than the speed of light on a connection with air-tight security? You could connect to a computer anywhere around the world in the blink of an eye and never have to worry about malicious activity. It seems impossible, right? Not necessarily. It could actually be done by using a quantum network. A true quantum network would be much faster than any connection we could implement with our current telecommunications hardware. In fact, a signal transferred over a true quantum connection wouldn’t take time to transfer whatsoever. It would literally arrive instantly, and would be sent using physical properties that dictate the mechanics of the entire universe. The implications of harnessing these phenomena are astounding. In a 2011 article written in by Lydia Leavitt it states that, “Researchers at the University of Copenhagen's Niels Bohr Institute have discovered what might be the key to completely secure data transfer, keeping particles ‘entangled’ for up to an hour. Until now, the link between two entangled systems could only be maintained for a fraction of a second. This development could enable a direct link between two systems of communication” (engadget.com, N.P.). This could mean incredible things for our communication systems. Don’t think that speed and convenience aren’t the only benefits we would reap either. There would be countless new tools and abilities that would come from perfecting this system. The quantum principle that this type of network is based on is called quantum entanglement. Entanglement was described by Albert Einstein as "spukhafte Fernwirkung", which means spooky action at a distance. The basic concept of entanglement is relatively simple. It isn’t quite so simple to understand, though. A brief explanation by Dave Jarvis says “When a photon (usually polarized laser light) passes through matter, it will be absorbed by an electron. Eventually, and spontaneously, the electron will return to its ground state by emitting the photon. Certain crystal structures increase the likelihood that the photon will split into two photons, both of them with longer wavelengths than the original. Keep in mind that a longer wavelength means a lower frequency, and thus less energy. The total energy of the two photons must equal the energy of the photon originally fired from the laser (conservation of energy). When the original photon splits into two photons, the resulting photon pair is considered entangled” (davidjarvis.ca, N.P.). The history of Quantum entanglement is an impressive stream of brilliant minds, hard work, and creativity. The development of quantum mechanics began around the seventeenth century when scientists proposed a wave theory about light. The next massively influential stage of its development was the study of black body radiation. The main players in this were: Gustav Kirchhoff, Ludwig Boltzmann, Max Planck, and Wilhelm Wien. Planck perfected the theory for black body radiation around 1896. That theory became Planck’s Law and set the course of quantum theory’s development. Some of the most impacting principles of quantum mechanics are the theory of relativity, Wave-particle duality, and quantum field theory.
The principle we’ll talk about here is quantum entanglement. It was initially researched for a critical paper in 1935 by Albert Einstein, Nathan Rosen, and Boris Podolsky. They determined that the current quantum description of the universe could not be considered complete. Later that year, Erwin Schrödinger coined “Verschränkung.” This is a term that means “entanglement.” He also gave us a great visual example the quantum concept when he came up with his infamous thought experiment involving alternate reality felines. In 1964, John Bell presented the mathematical proof that allowed experiments to rule out hidden variables. It showed that entanglement could be explained through purely local effects unless the proof was violated. Alain Aspect, a French physicist, later violated the proof in the strongest test done thus far. This confirmed that nonlocal effects do exist. This led Charles Bennett and Gilles Brassard to come up with an idea for quantum cryptography in 1984. It would use a photon’s state changes to make an encrypted key. Six years later, Bennett reported the first test model for key distribution using quantum mechanics. Bennett later proposed that the principles of quantum entanglement could theoretically teleport quantum information from one particle to another. This theory was verified in 1997 when it was tested by Anton Zeilinger. Anton set a record in 2007 for distance of controlled entanglement of photons. The record was 144 kilometers. In that same year Chao-Yang Lu set the record of entangled particles to six. One of the most recent leaps forward was in 2010. As reported in 75 Years of Entanglement, “Researchers observe new kinds of entanglement when linking multiple objects quantumly, quantum information is teleported a record 16 kilometers and teams find better ways to create and control entangled objects” (Witze, 2). This is the origin of the current model of a quantum network. Quantum networks work by teleporting information about the state of a photon without passing through space and time by pairing (entangling) it with another photon at a different location and reading the information from there. The problem is that if you try to read quantum information like a control signal (like a normal router would read a packet) the information stops existing. Luckily, the world has now seen its first quantum router. An article by Jamie Condliffe states, “The new device, offered up by Tsinghau University in China, creates a quantum photon that is in a superposition of two separate photons that are in horizontal and vertical polarized states. That quantum photon is then converted into two, lower power, photons, which both also share the same dual polarization. Then, a router can read data from one photon, which it destroys, and use the remaining one as the data signal” (N.P.). Another issue with quantum entanglement is that it is an incredibly fragile state. This problem was taken on by Xing-Can Yao and others at the University of Science and Technology of China. Many photons are usually produced for each successfully entangled pair in entanglement experiments,. The more pairs you have, the more difficult it is. They found that if they added an additional entangled pair of photons, it would take around ten hours to generate a set of eight photon pairs. They overcame this by using an optical scheme that increased the output of entangled particles. They then detected hundreds more entangled pairs at a rate of around nine an hour. This sufficed to undergo the tests that verified all eight of the photons were connected on a quantum level. This, alas, is not the final piece of the puzzle. There are still many obstacles in the way of a functional quantum network on a large scale. Ye Yeo addressed the problem of quantum noise interfering with quantum information protocols in his essay by saying, “Systems and processors can never be perfectly isolated from the surrounding world. Environmental influences always result in loss of coherence. These naturally become more serious when the quantum systems and operations are being scaled up in any eventual realization of quantum information processing” (Yeo, 1).
There are other types of quantum computing as well, though Quantum computers are still in their infancy. They use quantum properties, rather than binary (ones and zeros), to represent encoded data. Experiments have been carried out with a small number of qubits (or quantum bits). The qubits were used to carry out basic computing operations. In the future, quantum computers will be able to compute select types of problems much faster than current day computer systems can. Examples of one of these problems would be Shor’s algorithm or simulating a quantum many-body system. Another example of quantum computing is quantum key distribution. It is a variant of quantum cryptography. Quantum key distribution (QKD) works by two hosts set up shared key, without a having a third host getting any information about the key. Host one would encode bits of a key as quantum data then send that key data to host two. If host three tried to figure out the key, it would disrupt the message. This is usually used for encrypted communication.
The importance of working towards a perfected quantum network and other quantum computing is massively looked over in today’s culture. Quantum theory and quantum computing get miniscule amounts of media attention, whereas failing scientific endeavors are getting excess funding and publicity. A full understanding of quantum properties could lead to an infinite number of scientific and technological possibilities. Unfortunately, the quantum theory is rarely introduced before upper-level college physics classes. Therefore the majority of people (even those possessing an advanced degree) will not even learn the basics of quantum mechanics or the impact of the implications that lie in the properties of the theory. These quantum principles make up the fabric and core mechanics of our universe. The capabilities of fully harnessed quantum mechanics would change the world forever.

Works Cited
1 :Leavitt, Lydia. "Quantum Entanglement Could Mean Completely Secure Data Transfer." N.p., 21 Aug. 2011. Web.

2: Jarvis, David. "Quantum Entanglement." Weblog post. Quantum Entanglement. N.p., n.d. Web.

3: Witze, Alexandra. "75 Years Of Entanglement." Science News 178.11 (2010): 24-25. Academic Search Complete. 9 Dec. 2012. Web.

4: Condliffe, Jamie. "Scientists Have Made the World’s First Quantum Router." N.p., 3 Aug. 2012. Web.

5: Yeo, Ye. "Devastating Effects Of Quantum Noises And Noisy Quantum Operations On Entanglement And Quantum Information Protocols." AIP Conference Proceedings1363.1 (2011): 81-84. 9 Dec. 2012.