A Nightmare of an Eminent Person: A Supporter of the Copenhagen Interpretation Goes to Hell

This is a story about a dear friend of mine, Professor Gustav Klimtovich, who is a world-leading researcher in theoretical quantum physics. Gustav is based at an old Central European University which recently underwent a renaissance (climbing up 200 places on the Times Higher Education University list!) not in small part due to Gustav’s groundbreaking work in the foundations of quantum mechanics. To my great surprise, however, even an illustrious person like Gustav has nightmares and he told me about his recent one involving Hell and the Devil. Gustav’s story made such a strong impression on me that I decided to communicate it to you at once. I will tell it to you as he told it to me: in the first person (on his behalf).

I fell asleep one night and dreamt I died. Previously I had thought that it was impossible to dream about one’s own death, however, this clearly was not the case. Anyhow, despite the fact that I am a rather pious, church-going individual, I was being sent straight to Hell. I attributed this unfortunate occurrence to the fact that I had rejected too many good research papers from my competitors, which (one could indeed argue convincingly) might be morally questionable. I accepted my fate without resistance and didn’t worry much about going to Hell. How bad could it be?, I thought. But, little did I know…

At the gates of Hell, I was greeted by a funny looking fella. Goatee beard, sharp pointy ears (almost invisible as though glued to his skull), squinting grey eyes and, above all, he was really well dressed (clearly not a physicist, I surmised). I immediately assumed he was some kind of a porter, one of those that you encounter when you go to an Oxford College.

He asked me something unexpected though. If I was to be sent through a beam splitter, the fella said, which side of the beam splitter would I come out from? He is definitely a funny guy, I thought to myself. I said, if it was a fifty-fifty beam splitter, then I suppose that I would have an equal chance of coming out at either end. It’s simple, I elaborated further – it is just a direct application of the Born rule (for some reason I assumed that this guy would be familiar with the third postulate of quantum physics).

Alright, he said, let me escort you to meet his Majesty the Devil. This really was stranger still. I get asked a simple question and, upon answering it (correctly, I assumed), I immediately get to see The Big Guy. I wished real life was like that! Imagine answering one question correctly by your Research Funding Agency and immediately getting an interview with its Chief Executive. That would be nice, I mused. But then came a surprise.

He opened a door and we entered a room that looked like a standard atomic physics laboratory (an optical table with lots of laser, beam splitters, some fancy cryogenics, you know the kind of stuff). I always thought that experimental physics was the work of the Devil, but I never expected to encounter a firsthand piece of evidence of this fact. Now the fella says: if I give you two million qubits all prepared in an equal superposition of zero and one logical states, and if you measured them in that logical basis, what would you expect to see?

Is this guy for real? He asked me a similar question a while back, so why does he expect a different answer now. Despite being confused about his intentions, I nevertheless proceeded to answer. You’d expect to see one million in the state zero and one million in the state one, give or take a few thousand (I assumed that he was familiar with standard deviations too). OK, says he. The beauty of this room is that we don’t have to imagine. What you see in front of us is a quantum computer, with one billion qubits (and, no, we didn’t get it from Google. It is bona fide made-in-Hell). I will now prepare two million of the qubits in the said superposition and leave the room. You can then measure them one by one, he said to me, and see what happens.

I was game. I must admit I was very excited to see a fully functional large-scale quantum computer. My God, it is – after all – possible to make one (I had always thought that some kind of decoherence would prevent it, or some kind of Penrose-style induced collapse). It was easy for me to program the computer to execute the measurements (it’s a bit like running a Mathematica code – all us theoreticians know how to do that easily). To my great surprise, all qubits came out with the value zero.

The fella came back and must have seen that I was in shock. So?, he said. I said they all came up zero, which is statistically exceedingly unlikely. The fella was kind to let me repeat the experiment again. And again. And again. But not matter how many times I did it, all the qubits always came up in the logical state zero.

How can this be? Finally, I said to the fella: could it be that we are using a quantum computer to show that quantum physics is wrong? (I remember reading a Nature paper by Dr. Henrietta Grünberg saying something to that effect). No, said he categorically. It is your Copenhagen frame of mind that prevents you from seeing the truth, he told me.

What? How did he know I was a Copenhagen supporter? He must have read my papers. No, unlikely, but maybe he attended my lecture course on the foundations of quantum physics. No, wait, he does look familiar after all, maybe I have seen him at some conference or other. As I was desperately trying to figure all this out, the fella said: ‘You need to work with the hypothesis that the whole Hell is quantum. You and the quantum computer you have been operating are just part of an even bigger quantum computer (run ultimately by the Devil).’

What, the whole Hell is quantum?, I gasped. The Devil is a Many Worlder, programming the dynamics of Hell? He (I always assumed the Devil was a he, but, honestly, I am not that sure anymore) actually let me make all these measurements and he then run the Grover amplitude amplification algorithm on the whole lab to amplify the branch with all the zeroes to a 100 percent certainty. I was simply flabbergasted.

But much more than Devil’s experimental prowess, what spooked me the most is that I have been wrong all along regarding the interpretation of quantum physics. If the Devil is able to pull this off, Copenhagen cannot be right! I keep deterministically landing in the state that is exponentially unlikely according to Born, but instead of refuting quantum physics, this actually proved its validity!

I was desperate. God, why hast thou forsaken me? At that point, just as I uttered those words, everything around me came to a halt. Then it all vanished in a puff of smoke. There simply was nothing left. Not even the quantum vacuum.

Then I woke up. Lucky. It took me only a second to realise what had happened. I was right to be Copenhagen. There is after all a classical frontier. It is defined by God. He (again God surely is a he too) must have made me collapse into a single universe that makes sense and where I am not having nightmares about Hell, the Devil and Many Worlds. Phew. I always knew there must be the ultimate classical frontier. The universe cannot be in a gignormous quantum superposition, since it is, thankfully, always observed by God. God provides the necessary collapse needed to get rid of all the devilish quantum entanglements.

I was relieved. And, as I always do when I wake up, I turned on my radio. It was 10am, news time. The voice said, `Google has today announced its first one billion qubit quantum computer’. Damn it, I thought, I knew I should have bought more of their shares a couple of years back.

Vlatko.