THE QUANTUM SOURCE OF SPACE TIME

**Background. **We recently published a news story on how quantum entanglement can be used to bridge the theoretical gap between quantum mechanics and general relativity, based on the the work of Mark Van Raamsdonk, and his attempts to get the wider physics community to take these theories seriously.

**Design Challenge**. We felt a graphic was needed to help the reader visualise the complex theory behind the story. After discussion with the editor we decided to tackle the graphic in three parts, with each part explaining the three main theories in the story. (For all three parts, see sketches, second image above.)

Part 1. The first part was to give a visual grounding, a starting point from which a connection could be make between the idea of the universe of general relativity (containing gravity) and the abstract theories of quantum mechanics. To do this we needed to show the similarities between two diagrams: a hyperbolic tesselation diagram (showing how space distorts as it stretches out towards its infinite boudary) and a tensor network, which visualises the quantum entanglement connections between particles in a large system. We also added a basic explanation of quantum entanglement, based on this sketch by the editor.

Part 2. For the next part of the graphic we wanted to explain how the theory of entanglement is linked to space time, using the ideas introduced in the first part of the graphic, based on sketches made by Van Raamsdonk.

Part 3. In the final part of the graphic we would develop the previous concept further by showing the link between wormholes (connections through space time that link black holes) and quantum entanglement. To do this we would use a standard diagram of a wormhole, and link this to the earlier depiction of quantum entanglement.

**Visualising theoretical physics**. As ever with graphics about theoretical physics the challenges are numerous. First, visualising things that due to their scale, have no form. Next, getting the balance right between simplicity and correctness – how can we represent the elements in a basic way but still be essentially correct in what we are showing? And finally, having a narrative that runs through the graphic that isn’t confusing, and gives the reader a sense of having a basic understanding of a wider, more complex subject.

To do all of these things, it is important to have a strong understanding of the theory, and this involves digesting some mind-bending concepts!

**Final graphic.** In the final graphic, I decided to overlay the tessellation diagram and the tensor network diagram, to really emphasise the link between the two.

I simplified the entanglement diagram as much as possible so that as little space was taken up explaining this as possible.

For the next part, I duplicated the tensor network diagram to represent the quantum entanglement connecting two points in space. And in the final part I used the same icons to show entanglement as in the earlier explainer, to try to round of the explanation with this link.

I also decided on pulling out what to me were the most important points from the text using larger, bold font, so that these points weren’t lost in the complexity of the overall graphic, and so that the reader felt they were coming away understanding these key concepts.

-Nik Spencer