Richard Feynman once said, “If you think you understand quantum mechanics, then you don’t understand quantum mechanics.” While that may be true, it certainly doesn’t mean we can’t try. After all, where would we be without our innate curiosity?
To understand the power of the unknown, we’re going to untangle the key concepts behind quantum physics — two of them, to be exact (phew!). It’s all rather abstract, really, but that’s good news for us, because you don’t need to be a Nobel-winning theoretical physicist to understand what’s going on. And what’s going on? Well, let’s find out.
Laying the groundwork
We’ll start with a brief thought experiment. Austrian physicist Erwin Schrödinger wants you to imagine a cat in a sealed box. So far, so good. Now imagine a vial containing a deadly substance is placed inside the box. What happened to the cat? We cannot know to a certainty. Thus, until the situation is observed, i.e. we open the box, the cat is both dead and alive, or in more scientific terms, it is in a superposition of states. This famous thought experiment is known as the Schrödinger’s cat paradox, and it perfectly explains one of the two main phenomena of quantum mechanics.
Superposition dictates that, much like our beloved cat, a particle exists in all possible states up until the moment it is measured. “Observing” the particle immediately destroys its quantum properties, and voilà, it is once again governed by the rules of classical mechanics.
Now, things are about to get more tricky, but don’t be deterred — even Einstein was thrown-back by the idea. Described by the man himself as “spooky action at a distance”, entanglement is a connection between a pair of particles — a physical interaction that results in their shared state (or lack thereof, if we go by superposition).
Entanglement dictates that a change in the state of one entangled particle triggers an immediate, predictable response from the remaining particle. To put things into perspective, let’s throw two entangled coins into the air. Subsequently, let’s observe the result. Did the first coin land on heads? Then the measurement of the remaining coin must be tales. In other words, when observed, entangled particles counter each other’s measurements. No need to be afraid, though — entanglement is not that common. Not yet, that is.
The likely hero
“What’s the point of all this knowledge if I can’t use it?”, you may be asking. Whatever your question, chances are a quantum computer has the answer. In a digital computer, the system requires bits to increase its processing power. Thus, in order to double the processing power, you would simply double the amount of bits — this is not at all similar in quantum computers.
A quantum computer uses qubits, the basic unit of quantum information, to provide processing capabilities unmatched even by the world’s most powerful supercomputers. How? Superposed qubits can simultaneously tackle a number of potential outcomes (or states, to be more consistent with our previous segments). In comparison, a digital computer can only crunch through one calculation at a time. Furthermore, through entanglement, we are able to exponentially amplify the power of a quantum computer, particularly when comparing this to the efficiency of traditional bits in a digital machine. To visualise the scale, consider the sheer amount of processing power each qubit provides, and now double it.
But there’s a catch — even the slightest vibrations and temperature changes, referred to by scientists as “noise”, can cause quantum properties to decay and eventually, disappear altogether. While you can’t observe this in real time, what you will experience is a computational error. The decay of quantum properties is known as decoherence, and it is one of the biggest setbacks when it comes to technology relying on quantum mechanics.
In an ideal scenario, a quantum processor is completely isolated from its surroundings. To do so, scientists use specialised fridges, known as cryogenic refrigerators. These cryogenic refrigerators are colder than interstellar space, and they enable our quantum processor to conduct electricity with virtually no resistance. This is known as a superconducting state, and it makes quantum computers extremely efficient. As a result, our quantum processor requires a fraction of the energy a digital processor would use, generating exponentially more power and substantially less heat in the process. In an ideal scenario, that is.
A (new) world of possibilities
Weather forecasting, financial and molecular modelling, particle physics… the application possibilities for quantum computation are both enormous and prosperous.
Still, one of the most tantalising prospects is perhaps that of quantum artificial intelligence. This is because quantum systems excel at calculating probabilities for many possible choices — their ability to provide continuous feedback to intelligent software is unparalleled in today’s market. The estimated impact is immeasurable, spanning across fields and industries — from AI in the automotive all the way to medical research. Lockheed Martin, American aerospace giant, was quick to realise the benefits, and is already leading by example with its quantum computer, using it for autopilot software testing. Take notes.
The principles of quantum mechanics are also used to address issues in cybersecurity. RSA (Rivest-Shamir-Adleman) cryptography, one of the world’s go-to methods of data encryption, relies on the difficulty of factoring (very) large prime numbers. While this may work with traditional computers, which aren’t particularly effective at solving multi-factor problems, quantum computers will easily crack these encryptions thanks to their unique ability to calculate numerous outcomes simultaneously.
Theoretically, Quantum key distribution takes care of this with a superposition-based encryption system. Imagine you’re trying to relay sensitive information to a friend. To do so, you create an encryption key using qubits, which are then sent to the recipient over an optical cable. Had the encoded qubits been observed by a third party, both you and your friend will have been notified by an unexpected error in the operation. However, to maximise the benefits of QKD, the encryption keys would have to maintain their quantum properties at all times. Easier said than done.
Food for thought
It doesn’t stop there. The brightest minds around the globe are constantly trying to utilise entanglement as a mode of quantum communication. So far, Chinese researchers were able to successfully beam entangled pairs of photons through their Micius satellite over a record-holding 745 miles. That’s the good news. The bad news is that, out of the 6 million entangled photons beamed each second, only one pair survived the journey (thanks, decoherence). An incredible feat nonetheless, this experiment outlines the kind of infrastructure we may use in the future to secure quantum networks.
The quantum race also saw a recent breakthrough advancement from QuTech, a research centre at TU Delft in the Netherlands — their quantum system operates at a temperature over one degree warmer than absolute zero (-273 degrees Celsius).
While these achievements may seem insignificant to you and I, the truth is that, try after try, such groundbreaking research is bringing us a step closer to the tech of tomorrow. One thing remains unchanged, however, and that is the glaring reality that those who manage to successfully harness the power of quantum mechanics will have supremacy over the rest of the world. How do you think they will use it?