How do quantum computers use physics?
Traditional computers operate based on data that is encoded in a binary system. Essentially, each bit of data is represented in zeroes and ones only — no more, no less than the two forms. Hence, the binary computing system. However, there is a new generation of computers emerging on the horizon called quantum computing and it's taking computing systems beyond the normal binary.
Instead of just the zeroes and the ones, quantum computing depends on quantum bits or qubits. Quantum computing breaks the boundaries of traditional computing by allowing the information — coded in qubits — to have multiple states at once. This phenomenon, known as superposition, unlocks more computing power than previously imagined. Companies like IBM, Google and Microsoft have taken initial steps to invest in and adopt quantum computing.
Quantum computers break the laws of Newtonian physics by tapping into the science of quantum physics.
Imagine you were confronted with a locked door and had millions of identical-looking keys on your ring, with only one that worked. Using the digital computer method, you would have to try each one, one at a time, until you found the right one. Adding more circuits could increase your computing power, but you would still be stuck in the laws of physics and forced to try one key at a time. No matter how quickly you tried, it could still be a very long time before you got through.
Quantum computers, by contrast, break the laws of Newtonian physics by tapping into the science of quantum physics. In quantum physics, objects can exist in multiple states at the same time when you get down to the molecular level. A quantum computer attempts to tap into those strange properties at the molecular level and harness them to solve problems at the macro level where we all live, or at least where we perceive reality.
What makes them special is that instead of circuits, they use atoms or elections called quantum bits or qbits. The qbits can exist in a state called superposition where they represent a one and a zero, and all states in-between—at the same time. Quantum computers then attempt to string together qbits so they can be compared and correlated.
Now, you might be wondering, as we are all made up of these same atoms being used by quantum computers, why we don’t exist in multiple states at the same time, too?
The reason is that the state of superposition is very fragile. Almost anything can strip away those properties and imprison our atoms in the single state we call reality, which is probably a good thing for us. Beams of light, heat, soundwaves, vibration, air molecules or even radiation strip away the multiple states in a process called decoherence.
Quantum computers need to eliminate decoherence in order to induce superposition in their qbits. That is why they are built inside black boxes where no light or sound can penetrate. They are also shielded from radiation, kept in a vacuum and chilled down to almost absolute zero.
And you can’t even observe or monitor them as they work because any data leakage kills whatever equation they are working on. This also prevents any recording or analysis of their process, so you never really know how they arrived at their answer.
A comparison of classical and quantum computing
Classical computing relies, at its ultimate level, on principles expressed by Boolean algebra. Data must be processed in an exclusive binary state at any point in time or bits. While the time that each transistor or capacitor need be either in 0 or 1 before switching states is now measurable in billionths of a second, there is still a limit as to how quickly these devices can be made to switch state. As we progress to smaller and faster circuits, we begin to reach the physical limits of materials and the threshold for classical laws of physics to apply. Beyond this, the quantum world takes over. In a quantum computer, a number of elemental particles such as electrons or photons can be used with either their charge or polarization acting as a representation of 0 and/or 1. Each of these particles is known as a quantum bit, or qubit, the nature and behavior of these particles form the basis of quantum computing.
How powerful can quantum computers get?
While the digital computer might still be trying each key one at a time, a powerful quantum computer could instead use superposition to try all the keys at the same time and instantly open the lock. It doesn’t even really matter how many possible keys exist. That’s bad news for encryption, and why NIST is so worried about protecting government secrets by trying to develop some type of quantum-resistant defense.
