Question - how can you be quicker?
Well, how about being in two places at once. When we drill down to the quantum level, things on a particle scale look very different to how we normally perceive them. Richard P. Feynman once said: "Things on a very small scale behave like nothing you have any direct experience about... or like anything that you have ever seen."
Traditional computers use bits as a basic digital unit of information, either a zero or a one. There only two possible states. However, quantum computing uses qubits, which can either be zero, one, zero and one, or an infinite number of combinations between.
In theory, at least, if quantum computers started to take over from silicon based integrated circuits as the building blocks of computers, Moore's Law, the applications of which mean that computers double in speed every 18 months or so, would begin to look positively sluggish. Some say that quantum computers could be a billion times faster than a PC today.
Except that they are only faster and superior in certain scenarios, such as dealing with and processing a huge volume of numbers. In other words, they must be pretty good for high frequency trading.
So what does this mean?
Once the technology is working, new opportunities will emerge for arbitrage trading at a speed that makes the current pace of things look amateur. But if quantum computing was to become widespread, this would lead to the cost of of quantum computing falling, in turn meaning that more firms will operate on a high-frequency trading model. Thus, the smallest of imperfections that the HFT community current has to deal with, for example 'flash crashes', will possibly be affecting the industry on a much bigger scale with much bigger consequences.
The regulators will need quantum computers to try and keep track of what is happening, and ultimately may conclude that they have to wrap high frequency trading in cotton wool, regulating the advantages of quantum computing away.