An album of one-minute headcam clips climbing the Aiguilles d’Entrèves traverse (3,600m, AD-) via Glacier du Géant, Mont Blanc massif, France. Route description: theCrag.
All posts by Peter Rohde
An introduction to graph states
What is a graph state?
One especially useful class of quantum states is graph states, also known as cluster states. As the name suggests, a graph state |G\rangle is associated with a graph,
G=(V,E),
where the vertices (v\in V) represent qubits initialised into the
|+\rangle = (|0\rangle+|1\rangle)/\sqrt{2}
state, and edges (e\in E) represent the application of controlled-phase (CZ) gates between respective vertices, where,
\mathrm{CZ}=\mathrm{diag}(1,1,1,-1).
A graph state can therefore be expressed as,
|G\rangle = \left[ \prod_{e\in E} \mathrm{CZ}_e \right] |+\rangle^{\otimes |V|}.
Since CZ gates are diagonal and therefore commute with one another, the order in which they are applied is irrelevant, meaning there is great flexibility in the preparation of graph states and room for parallelisation in the application of the required CZ gates.
New paper: Proof-of-work consensus by quantum sampling
Our new paper on using boson-sampling as a basis for distributed blockchain consensus algorithms is available here.
Abstract: Since its advent in 2011, boson-sampling has been a preferred candidate for demonstrating quantum advantage because of its simplicity and near-term requirements compared to other quantum algorithms. We propose to use a variant, called coarse-grained boson-sampling (CGBS), as a quantum Proof-of-Work (PoW) scheme for blockchain consensus. The users perform boson-sampling using input states that depend on the current block information, and commit their samples to the network. Afterward, CGBS strategies are determined which can be used to both validate samples and to reward successful miners. By combining rewards to miners committing honest samples together with penalties to miners committing dishonest samples, a Nash equilibrium is found that incentivizes honest nodes. The scheme works for both Fock state boson sampling and Gaussian boson sampling and provides dramatic speedup and energy savings relative to computation by classical hardware.
How do photonic Bell measurements work?
Entangling Bell measurements are an essential ingredient in many photonic quantum technologies. In optical quantum computing they are employed as fusion gates to create edges in graph states, while in quantum communications protocols they may be used to implement entanglement swapping in quantum repeater networks (entanglement distribution networks) for extending the range of entanglement links.
In this post I’ll describe how this very simple optical circuit works and address some of the nuances and common misconceptions surrounding it.
Continue reading How do photonic Bell measurements work?
Response to “Pause Giant AI Experiments: An Open Letter”
I completely disagree with the open letter signed by Elon Musk and numerous other luminaries in which they advocate a moratorium on advancing AI so that time can be taken to consider the implications and risks associated with this technology.
Continue reading Response to “Pause Giant AI Experiments: An Open Letter”
New track – Naso del Liskamm
My new track “Naso del Liskamm” is now available on Spotify, SoundCloud and other major streaming services.
New track — Zinalrothorn
My new track “Zinalrothorn” is now available on SoundCloud.
MoodSnap now in Spanish
We’re delighted to announce that MoodSnap mood diary is now localised to the Spanish language. We’re incredibly excited that all our Spanish-speaking friends can now use MoodSnap in their native language.
Thank you to Melany Nadine Monroy Icaza for providing the translation and Christian Ronald Cresci for proof-checking.
Terminally Quantum podcast series
Together with Alexandra Dickie we’re pleased to announce our new quantum podcast series Terminally Quantum, hosted at The Quantum Terminal in Sydney, Australia. Our first episode, featuring Prof Peter Turner, CEO of the Sydney Quantum Academy, is now available on Spotify and Apple Podcasts.
MoodSnap jetzt in Deutsch
One of the goals of my free mood diary app MoodSnap is to make it accessible to as many people as possible. Today I’m pleased to announce that MoodSnap has been fully localised for the German language, with more languages in progress.
You can get MoodSnap on the Apple AppStore and find out more at the MoodSnap homepage.