To understand how we might acheive coherence, it is first necesary to understand how decoherence is brought about. This is if we begine by presuming a quantum realm in the beginning wherein the clasic world emerges latter. This is how many think when contemplating quantum mechanics (qm). As we know, qm says that unless a quantum system interacts with the classic word (including classic observers), the qm systems remains in a strange superposition of states that propagates as waves. So if the classic world is neaded to form the particles (isolate objects), and the particles themselves forms the clasic world, it raises an egg chicken paradox. Where did the clasic world came from then? The answer is that the quantum world decoheres. That is to say the waves from all the particles that sum up to form objects donnot all vibrate in a synchroniced manner in every place. So they cancel themselves in some places forming the ’empty spaces seperating objects’.
The secret to acheiving quantum coherence would perharps come if we are to understand how this coherence is brought about in microscopic world. In classic world, we understand that waves emanating from the same source are always coherent. To understand this, drop a pebble in a pool of water. Then you will observe some almost perfectly circular concentric rings centred at the source and radiating away from it. Since they form perfect circles, regions of water equidistant from the source are always vibrating synchronously, no matter how far apart from each other. So it behaves as though those distant locations, connected by the circumfrence of a given concentric ring are instantaneously connected to each other!
One might be tempted to think tha quantum coherence is brought about by such coincidence that results from the waves emanating from the sorce. Though it is corelated to having a common source, quantum coherence is actually brought about by a strange instantaneous communication between distant parts of the quantum ocean! This phenomenon is the so called quantum nonlocality. For instance, if a wave was radiating out in all directions, then before observation, various portions of the quantum ocean are undulating. However when the ocean is observed, all other regions of the ocean, apart from where the particle is found, freezes instantaneously! It is typical magics that are happening in quantum ocean!
So then what brings about quantum coherence is a strange, intelligent like signal telling different regions in the ocean how to dance! It is a sort of a cosmic drum beater or a lead guitarist synchronising the dances! So it is just upto understanding and talking the language of particles! Quantum decoherence comes about because there isn’t realy a single commander in the ocean. Lets say there are 3 particles in the cosmos located at 3 different locations. Calle them A, B and C. Now if originaly, B is quantum coherent with A and are thus both vibrating in synch at some frequency, C might be vibrating at another frequency hence decoherently but still would wanna get entangled with the system of A and B. So if C is nearer to B, it will influence B to dance to its own music, forcing it to compromise abit