Spooky Action: A Primer on Quantum Mechanics, Entanglement & Teleportation… in 1,000 Words or Less

Posted: June 5, 2014 in The Cyberpunk Chronicles

“I don’t like it and I’m sorry I ever had anything to do with it.”

— Erwin Schrödinger, on his contributions to Quantum Mechanics

A few days ago, Dutch scientists at the Delft University of Technology reported having successfully teleported information between two entangled quantum bits ten feet apart, with no reported degradation. As an pundit of the physical sciences, I have been very excited by this news, imagining several possibilities that could very well be realized as consequences of this achievement. Mind you, this has not been the first time quantum teleportation has been accomplished. Nor is it a record-breaker, by any account (the current record is 143 km, or 89 miles, according to this group). But it is said to be the most successful transfer of information over a significant distance.

Before I continue, I will hash out a few concepts (in my snarkiest possible tone) before you get all glazy-eyed on me. I’d rather explain them in terms I understand, because a lot of the sources out there are vague or altogether bogus:

qubit

A quantum bit, or “qubit” is a quantum analogue of the classical bit. Because you’ll ask, a “bit” is a basic unit of information in computing. Bits are binary, meaning they can only have a value of zeroes and ones. Bits are the building blocks of the information you are reading on this blog right now. Each letter of the alphabet corresponds to a cluster of bits (also known as a byte), corresponding to a certain arrangement of 0’s and 1’s. For example, the letter “A” in the ASCII table has a binary pattern of 01000001; “B” is 01000010… you get the idea. In classical computing, a bit can only be a 0 or a 1. In quantum computing, a qubit can be 0, 1, or both at the same time. This last concept of simultaneity is known as Superposition in Quantum Mechanics. Physically, a qubit can be any subatomic unit of matter that can exhibit such a duality of states, such as an electron or a photon.

Superposition Schrodinger's Cat

An electron has an intrinsic property called spin (associated with its magnetic polarization). By Pauli’s Exclusion Principle, only two electrons can coexist at any given state, but with opposing ends of said state. So in any given state (an orbital in an electron, a diamond confinement cell, etc.), you can only have one electron spinning “up” and one electron spinning “down.”  Sounds simple enough? Good. Your head’s about to get blown up some more.

spin

Now electrons are infinitessimally small, see, so that any attempt to “look” at them means that their a) momentum will be disturbed, or b) their position changes. Heisenberg’s Uncertainty Principle at work. Think of a pea bullet striking a static marble. Similarly, an individual electron struck by a photon would bounce away, thwarting any attempt to accurately measure it.  However, by this gnarley concept called Quantum Entanglement, we can bypass the Uncertainty Principle and obtain the information we need, without disturbing the electron in question. Well, sort of. During entanglement, two or more particles with opposing ends of a quantum state are confined, and we are able to determine the sum state of the system. So if you are getting a magnetic value of “0,” you can be confident that you have two electrons, of which one with a spin-up value of +1/2, the other with -1/2. Does it matter which one’s which? By quantum entanglement, not necessarily.

feature1-fig3

This is when Quantum Teleportation comes into play. A “simple” setup of a quantum teleportation would involve a photon, or a stream of photons, that are split so that one set is polarized horizontally, the other vertically; the photons are already entangled. Without identifying either one, i.e., measuring its state, both are separated a certain distance from each other. A segment of information is pumped into the home photon. The photon is observed, revealing its state. As a result, the enclosed information is destroyed. However, the observer communicates the revealed state to the party holding the other photon. Armed with this knowledge, the receiving end measures the away photon accordingly, which then reproduces the conditions for the other photon. In measuring the away photon, the information lost by the local photon manifests. The Delft experiment was essentially the same, except that electrons confined in diamond cells were used, instead of photons. Because electrons are much slower than photons, they are easier (more or less) to capture and modulate, improving the efficiency of information exchange. For a really cool infographic, check out the New York Times’ superb presentation here.

I won’t even mention anything about the whole “Einstein was wrong” spooky science cliche that just about every news article on the planet is trumpeting about. It is indeed spooky, because it seems to violate most laws of physics. In a way, it does; in reality, however, it does not. So far as we’re concerned, it’s only the information that’s been communicated from one end of the link to another. However, the vessels of communication still have to be physically transported from one end of the universe to another. So the photons won’t be violating the laws of relativity anytime soon in this case.

I can see why Einstein would get so worked up about quantum entanglement. If information, which hitherto had been communicated via the electromagnetic spectrum could now be instantaneously accessible, that implies some sort of superluminal travel. However, the information doesn’t so much travel as it manifests from one qubit to another, as if they were inextricably linked by an invisible psychic link. That’s the best analogy I can think of for quantum teleportation. The only way this could happen, though, is if the photons were homogenous enough in every way – except polarity. They have to be two equal but opposite sides of the same quantum coin, so to speak.

images

So there it is! Quantum mechanics, entanglement, and teleportation — all in a nutshell.  Next time, I’ll be talking about what kind of interesting applications we could see in the future, once all this technology has been perfected. Until then, stay spooky!

Copyright © 2014 The Anabases

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  1. […] Spooky Action: A Primer on Quantum Mechanics, Entanglement & Teleportation… in 1,000 Words… […]

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