The Quantum World- Error Correction

 A major disruptor in technology is quantum computing. It can actually turn out to be a bigger game changer than other technologies such as AI, blockchain, etc. The reason the others at the fundamental hardware level are nothing more than a string of 0's and 1's. Quantum computing changes the very fundamental way of how a computer works. 

For example imagine you toss a coin. If you let the coin fall and observe it, it will either be either heads or tails. Now imagine if you spin the coin on the table. It is difficult to tell whether the coin is heads or tails. In a way you can say it is both. The reason why quantum computers are powerful is because of this one property(although not limited to it). A computer has a bit which can be either 0 or 1. 0 implies turned off and 1 implies turned on. A quantum computer has qubits which can be 00 ,01, 10 and 11. These might not seem significant when you have very few qubits compared to bits but when increased they have a massive increase. Moreover qubits have this property of entanglement which further increases the computing power. 

Although currently it is in it's infancy stage the field is growing exponentially. A major challenge of quantum computing is that qubits need to be nearly kept in a space type environment for them to function properly. Moreover simply using a larger number of qubits would not necessarily increase the computation power as any process to determine the state of a qubit would result in decoherence.  

Now why quantum computers need to be kept in an isolated environment. I will give an example. Consider a classical computer has 3 copies of a bit. The values of the bit is 1. Now suppose due to some external factors the 3rd copy becomes 0. However, the computer is governed by a logic that all the copies should be 1. It checks the copies pairwise like 1-2, 2-3 and 1-3. It sees that the third copy is different compared to the 1st and 2nd one and hence changes the 3rd copy. This leads to redundancy but it also ensures the computer executes the correct instructions and there would be no errors. This method was formulated by the famed mathematician Von Neumann.

Unfortunately quantum computers don't have this ability due to the basic fundamentals of quantum mechanics. We cannot measure the state of a qubit as that would cause it to lose its quantum mechanical property. Basically if a qubit changes you have to determine which one changes without looking albeit a guess. This is because when one qubit changes it changes the other ones connected to it due to entanglement i.e. even its copy would change. 

The current method involves connecting extra qubits and entangle them with the ones which are performing the computation. Thus they can then observe the extra bit and infer whether the original bit lost its entanglement and then use microwaves to correct it. However a major problem is that qubits can not only bit flip but also phase flip which means they have an angle property to them as well. 

This is one of the main research area in the field of quantum computing. There have been method discussed but they are currently impossible to realize.  

However, there may be a method to correct this problem. It seems like a far fetched idea and I am not exactly sure if its allowed in physics. Since we have achieved phenomenal success in making millions of classical bits what if we could somehow express the state of a qubit in terms of classical bits. For example a qubit with 00 could somehow be encoded in 2 classical bits as 0 and 0 . Another couple of bits could denote its phase. In this manner we could then observe the change in the classical bits and infer whether the qubit has changed. It may not be possible as I haven't heard of classical computers operating at 0K but if somehow this is made to work a major breakthrough in quantum computing would occur and computing as we know would change forever.