Just when you think you understand quantum physics..

On and off, I guess I have been seriously fretting about the meaning of quantum mechanics, the powerful and hugely successful theory of the subatomic world, for over a quarter of a century. Now you might be thinking I am just a bit slow on the uptake – surely by now, as a practising theoretical physicist, I should feel comfortable about the mathematical formulation developed in the 1920s and which explains so beautifully how the building blocks of our universe fit together. After all, it underlies much of modern physics, chemistry and, increasingly likely according to the latest research, biology too. And trust me, we cover loads of quantum material in our undergraduate degree at Surrey.

But the weird thing about quantum mechanics – and, trust me, this stuff is nothing if not weird – is that we can get by perfectly well by using it to describe the world without having to spend sleepless nights trying to figure out how that atom can be in two places at once or an electron can spin clockwise and anticlockwise at the same time.

So it has come as a bit of a surprise to me to discover a new take on the meaning of quantum mechanics. Technically, it is called ‘weak measurement and post-selection’, but basically it is do with events in the future seemingly affecting events in the past. Yes, ‘huh??’ indeed.

I must get to the bottom of this. Is it profound or just another crazy interpretation of a crazy theory? I’ll report back with any progress.