How can we design experiments in quantum physics? Generally, the strategy involves using the vast knowledge amassed by quantum physics researchers and combining this with our intuitions and our creativity. This method has been fantastically successful over the years and has given us experiments that help unlock both the technological and the foundational magic of quantum physics. But it is not always easy. Quantum physics is notoriously counter-intuitive, so sometimes our intuitions are not a good guide for how best to design an experiment. And sometimes past experience is not always the best guide to creating novel new designs, particularly when our experiments intend to probe a new and untested area. But how else might we design quantum experiments? In a previous post we introduced a method we are developing that utilises techniques from AI, machine learning and meta-heuristics to design quantum experiments. In effect, we are letting computers design experiments for us.
To be more specific, our task is the following:
Given a set of quantum-optics experimental equipment, what is the best way of arranging the apparatus to create a quantum state with certain desirable properties? Continue reading
In recent years, there has been increasing concern that sometime in the future a super-intelligent AI will rise up, take over the world, and destroy all humanity. Is this a real concern? Or is it over-hyped science fiction, with no reasonable connection to reality? In this blog I will first argue that super-intelligence is possible, and then argue that if such an entity is created, it is a genuine possibility that it will indeed exterminate us all!
Why many worlds?
Quantum mechanics is often presented as being “our most successful theory ever”. Despite 100 years of stringent experimental tests it has never been proved wrong. It has been confirmed to an accuracy of 1 part in 1012 and has even now been tested in space-based experiments. It underlies much of modern technology, including pretty much the whole information and computing industry. And it has predictive power in an extreme range of scenarios, from the smallest constituents of our universe to a fraction of a second after the Big Bang. For these reasons, it seems reasonable to assume that quantum mechanics is correct, and does not need to be modified, at least not yet.
We can then ask the question: If quantum mechanics is correct, then what does it tell us about the universe? But before answering this, we should probe whether this is a reasonable question in the first place. Continue reading
This blog post follows on from a previous post, “What does quantum mechanics tell us about reality”, in which I tried to give a balanced and non-technical overview of some of the interpretations of quantum mechanics. In this post I will take a different approach: this will be a slightly biased, critical, and more technical follow-up. I recommend reading the earlier post first, but those already familiar with the interpretations of quantum mechanics should be able to dive straight into this.
In the Schrödinger’s cat thought experiment, a cat is placed in a box with a device that contains a radioactive atom and a vial of poison. If the atom decays, then the device is designed to release the poison, thus killing the cat. It is now well known that such an atom can be put into a state in which it has decayed, and not decayed simultaneously – this is known as a superposition state. Now, if this system is studied using the central equation in quantum mechanics, the Schrödinger equation, then the following result will be found: if the atom is in a superposition state, then this will lead to the cat being in a superposition state. The cat will be dead and alive simultaneously! Now suppose you open the box – what will you find? The Schrödinger equation again predicts that, if the cat was in a superposition of being dead and alive, then when you open the box you will also enter into a superposition. You will be in a superposition of either seeing the dead cat, whilst simultaneously seeing the alive cat.
How much coal do I need to put into my steam engine to get to Glasgow? How efficient can I make my power station? What’s the best way to cool down a cup of tea? The fundamental answers to these questions lies within the field of thermodynamics.
On the other side of the spectrum, scientists are asking seemingly disparate questions within the field of quantum information. How much entanglement do I need to pass on this message? How can I stop my quantum computer from losing its quantum-ness? What’s the best way I can make a quantum superposition?
Now it may seem that there can be no possible link between the answers to these questions. That a steam engine has nothing to do with quantum entanglement, well that is mostly true. However, all of questions are concerned with the same problem, the extractability and conservation of a given resource. On the thermodynamic scale, engineers want to know how heat and work behave. On the quantum scale, theorists and experimentalists alike are interested in defining and conserving the quantum-ness of a given system.
In order to bridge a gap between these fields, Continue reading
In this blog post I will introduce a core philosophical issue at the heart of quantum mechanics, and some of the most popular resolutions to this problem. This will be a non-technical introduction – I will try to avoid jargon and unnecessary details. But for those who like the gritty details, a second blog post will soon follow in which I will give a more technical and thorough (but also slightly biased) discussion of the same issues.
I first came across the Entanglement picture about 11 years ago. Nearing the end of my year-long visit to the Centre for Quantum Computation in Cambridge (UK), I was returning to Salerno (Italy) to start working on my PhD thesis. As my dissertation was entitled Entanglement of Gaussian states, I decided to include some pictures related to (quantum) entanglement at the beginning of each part. The first few hits for “entanglement” found at the time on Google Images eventually made the cut (check the final version at https://arxiv.org/abs/quant-ph/0702069) However, one of the images in particular captured my imagination – and stole my heart – so much that I chose it for the best spot: Part II, showcasing the bulk of my original results on bipartite entanglement. The image was a relatively low-res photo of a painting entitled, quite aptly, Entanglement, and taken from the website of its creator, American artist Pamela (Pam) Ott: http://www.hottr6.com/ott/.