Photon polarization Updated 2025-07-16
The knowledge that light is polarized precedes the knowledge of the existence of the photon, see polarization of light for the classical point of view.
The polarization state and how it can be decomposed into different modes can be well visualized with the Poincaré sphere.
One key idea about photon polarization is that it carries angular momentum. Therefore, when an electron changes orbitals in the Schrödinger equation solution for the hydrogen atom, the angular momentum (as well as energy) change is carried out by the polarization of the photon!
- clear animations showing how two circular polarizations can make a vertical polarization
- a polarizer can be modelled bra operator.
- light polarization experiments are extremely direct evidence of quantum superposition. Individual photons must be on both L and R states at the same time because a V filter passes half of either L or R single photons, but it passes all L + R photons
Poincaré sphere Updated 2026-08-21
In it, each of the six sides has a clear and simple to understand photon polarization state, either of:
The sphere clearly suggests for example that a rotational or diagonal polarizations are the combination of left/right with the correct phase. This is clearly explained at: Video "Quantum Mechanics 9b - Photon Spin and Schrodinger's Cat II by ViaScience (2013)".
Photonics equipment Updated 2025-07-16
Photomultiplier tube Updated 2025-07-16
Can be used to detect single photons.
Richard Feynman likes them, he describes the tube at Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979) at one point.
It uses the photoelectric effect multiple times to produce a chain reaction. In particular, as mentioned at youtu.be/5V8VCFkAd0A?t=74 from Video 1. "Using a Photomultiplier to Detect single photons by Huygens Optics" this means that the device has a lowest sensitive light frequency, beyond which photons don't have enough energy to eject any electrons.
Silicon photomultiplier Updated 2025-07-16
Here is a vendor showcasing their device. They claim in that video that a single photon is produced and detected:
Concrete device described at: Video "How to use an SiPM - Experiment Video by SensLTech (2018)".
Ladner's Theorem Updated 2025-07-16
PromethION Updated 2025-07-16
Oxford Nanopore MinION Updated 2026-08-21
One of the sequencers made by Oxford Nanopore Technologies.
The device has had several updates since however, notably of the pore proteins which are present in the critical flow cell consumable.
Official documentation: nanoporetech.com/products/minion (archive)
The following images of the device and its peripherals were taken during the experiment: Section "How to use an Oxford Nanopore MinION to extract DNA from river water and determine which bacteria live in it".
Top view of a closed Oxford Nanopore MinION
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Side view of an Oxford Nanopore MinION
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Top view of an open Oxford Nanopore MinION
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Loxbridge Updated 2025-07-16
Night climbing Updated 2025-07-16
- www.varsity.co.uk/features/24648 ‘It felt impossibly romantic’: the nightclimbers of Cambridge by Varsity (2022)
IonQ Updated 2025-07-16
- youtu.be/9aOLwjUZLm0?t=1216 superconducting qubits are bad because it is harder to ensure that they are all the same
- youtu.be/9aOLwjUZLm0?t=1270 our wires are provided by lasers. Gives example of ytterbium, which has nice frequencies for practical laser choice. Ytterbium ends in 6s2 5d1, so they must remove the 5d1 electron? But then you are left with 2 electrons in 6s2, can you just change their spins at will without problem?
- youtu.be/9aOLwjUZLm0?t=1391 a single atom actually reflects 1% of the input laser, not bad!
- youtu.be/9aOLwjUZLm0?t=1475 a transition that they want to drive in Ytterbium has 355 nm, which is easy to generate TODO why.
- youtu.be/9aOLwjUZLm0?t=1520 mentions that 351 would be much harder, e.g. as used in inertially confied fusion, takes up a room
- youtu.be/9aOLwjUZLm0?t=1539 what they use: a pulsed laser. It is made primarily for photolithography, Coherent, Inc. makes 200 of them a year, so it is reliable stuff and easy to operate. At www.coherent.com/lasers/nanosecond/avia-nx we can see some of their 355 offers. archive.ph/wip/JKuHI shows a used system going for 4500 USD.
- youtu.be/9aOLwjUZLm0?t=1584 Cirac and Zoller proposed the idea of using entangled ions soon after they heard about Shor's algorithm in 1995
- youtu.be/9aOLwjUZLm0?t=1641 you use optical tweezers to move the pairs of ions you want to entangle. This means shining a laser on two ions at the same time. Their movement depends on their spin, which is already in a superposition. If both move up, their distance stats the same, so the Coulomb interaction is unchanged. But if they are different, then one goes up and the other down, distance increases due to the diagonal, and energy is lower.
- youtu.be/9aOLwjUZLm0?t=1939 S. Debnah 2016 Nature experiment with a pentagon. Well, it is not a pentagon, they are just in a linear chain, the pentagon is just to convey the full connectivity. Maybe also Satanism. Anyways. This point also mentions usage of an acousto-optic modulator to select which atoms we want to act on. On the other side, a simpler wide laser is used that hits all atoms (optical tweezers are literally like tweezers in the sense that you use two lasers). Later on mentions that the modulator is from Harris, later merged with L3, so: www.l3harris.com/all-capabilities/acousto-optic-solutions
- youtu.be/9aOLwjUZLm0?t=2119 Bernstein-Vazirani algorithm. This to illustrate better connectivity of their ion approach compared to an IBM quantum computer, which is a superconducting quantum computer
- youtu.be/9aOLwjUZLm0?t=2354 hidden shift algorithm
- youtu.be/9aOLwjUZLm0?t=2740 Zhang et al. Nature 2017 paper about a 53 ion system that calculates something that cannot be classically calculated. Not fully controllable though, so more of a continuous-variable quantum information operation.
- youtu.be/9aOLwjUZLm0?t=2923 usage of cooling to 4 K to get lower pressures on top of vacuum. Before this point all experiments were room temperature. Shows image of refrigerator labelled Janis cooler, presumably something like: qd-uki.co.uk/cryogenics/janis-recirculating-gas-coolers/
- youtu.be/9aOLwjUZLm0?t=2962 qubit vs gates plot by H. Neven
- youtu.be/9aOLwjUZLm0?t=3108 modular trapped ion quantum computer ideas. Mentions experiment with 2 separate systems with optical link. Miniaturization and their black box. Mentions again that their chip is from Sandia. Amazing how you pronounce that.
NQIT Updated 2025-07-16
Oxford Ionics Updated 2025-07-16
This job announcement from 2022 gives a good idea about their tech stack: web.archive.org/web/20220920114810/https://oxfordionics.bamboohr.com/jobs/view.php?id=32&source=aWQ9MTA%3D. Notably, they use ARTIQ.
Quantinuum Updated 2025-07-16
Merger between Cambridge Quantum Computing, which does quantum software, and Honeywell Quantum Solutions, which does the hardware.
Universal Quantum Updated 2025-07-16
As of 2021, their location is a small business park in Haywards Heath, about 15 minutes north of Brighton[ref]
Funding rounds:
- 2022:
- 67m euro contract with the German government: www.uktech.news/deep-tech/universal-quantum-german-contract-20221102 Both co-founders are German. They then immediatly announced several jobs in Hamburg: apply.workable.com/universalquantum/?lng=en#jobs so presumably linked to the Hamburg University of Technology campus of the German Aerospace Center.
- medium.com/@universalquantum/universal-quantum-wins-67m-contract-to-build-the-fully-scalable-trapped-ion-quantum-computer-16eba31b869e
- 2021: $10M (7.5M GBP) grant from the British Government: www.uktech.news/news/brighton-universal-quantum-wins-grant-20211105This grant is very secretive, very hard to find any other information about it! Most investment trackers are not listing it.The article reads:Interesting!
Universal Quantum will lead a consortium that includes Rolls-Royce, quantum developer Riverlane, and world-class researchers from Imperial College London and The University of Sussex, among others.
A but further down the article gives some more information of partners, from which some of the hardware vendors can be deduced:The consortium includes end-user Rolls-Royce supported by the Science and Technology Facilities Council (STFC) Hartree Centre, quantum software developer Riverlane, supply chain partners Edwards, TMD Technologies (now acquired by Communications & Power Industries (CPI)) and Diamond Microwave
- Edwards is presumably Edwards Vacuum, since we know that trapped ion quantum computers rely heavily on good vacuum systems. Edwards Vacuum is also located quite close to Universal Quantum as of 2022, a few minutes drive.
- TMD Technologies is a microwave technology vendor amongst other things, and we know that microwaves are used e.g. to initialize the spin states of the ions
- Diamond Microwave is another microwave stuff vendor
www.riverlane.com/news/2021/12/riverlane-joins-7-5-million-consortium-to-build-error-corrected-quantum-processor/ gives some more details on the use case provided by Rolls Royce:The work with Rolls Royce will explore how quantum computers can develop practical applications toward the development of more sustainable and efficient jet engines.This starts by applying quantum algorithms to take steps to toward a greater understanding of how liquids and gases flow, a field known as 'fluid dynamics'. Simulating such flows accurately is beyond the computational capacity of even the most powerful classical computers today.This funding was part of a larger quantum push by the UKNQTP: www.ukri.org/news/50-million-in-funding-for-uk-quantum-industrial-projects/ - 2020: $4.5M (3.5M GBP) www.crunchbase.com/organization/universal-quantum. Just out of stealth.
Co-founders:
- Sebastian Weidt. He is German, right? Yes at youtu.be/SwHaJXVYIeI?t=1078 from Video 3. "Fireside Chat with with Sebastian Weidt by Startup Grind Brighton (2022)". The company was founded by two Germans from Essex!
- Winfried Hensinger: if you saw him on the street, you'd think he plays in a punk-rock band. That West Berlin feeling.
Homepage points to foundational paper: www.science.org/doi/10.1126/sciadv.1601540
Universal Quantum emerges out of stealth by University of Sussex (2020)
Source. Explains that a more "traditional" trapped ion quantum computer would user "pairs of lasers", which would require a lot of lasers. Their approach is to try and do it by applying voltages to a microchip instead.- youtu.be/rYe9TXz35B8?t=127 shows some 3D models. It shows how piezoelectric actuators are used to align or misalign some plates, which presumably then determine conductivity
Quantum Computing webinar with Sebastian Weidt by Green Lemon Company (2020)
Source. The sound quality is to bad to stop and listen to, but it presumaby shows the coding office in the background.Fireside Chat with with Sebastian Weidt by Startup Grind Brighton (2022)
Source. Very basic target audience:- youtu.be/SwHaJXVYIeI?t=680 we are not at a point where you can buy victory. There is too much uncertainty involved across different approaches.
- youtu.be/SwHaJXVYIeI?t=949 his background
- youtu.be/SwHaJXVYIeI?t=1277 difference between venture capitalists in different countries
- youtu.be/SwHaJXVYIeI?t=1535 they are 33 people now. They've just setup their office in Haywards Heath, north of Bristol.
Alice&Bob Updated 2025-07-16
About their qubit:
- alice-bob.com/2023/02/15/computing-256-bit-elliptic-curve-logarithm-in-9-hours-with-126133-cat-qubits/ Computing 256-bit elliptic curve logarithm in 9 hours with 126,133 cat qubits (2023). This describes their "cat qubit".
Google Quantum AI Updated 2025-07-16
The "AI" part is just prerequisite buzzword of the AI boom era for any project and completely bullshit.
According to job postings such as: archive.ph/wip/Fdgsv their center is in Goleta, California, near Santa Barbara. Though Google tends to promote it more as Santa Barbara, see e.g. Daniel's t-shirt at Video "Building a quantum computer with superconducting qubits by Daniel Sank (2019)".
IBM Quantum Computing Updated 2025-07-16
The term "IBM Q" has been used in some promotional material as of 2020, e.g.: www.ibm.com/mysupport/s/topic/0TO50000000227pGAA/ibm-q-quantum-computing?language=en_US though the fuller form "IBM Quantum Computing" is somewhat more widely used.
They also internally named an division as "IBM Q": sg.news.yahoo.com/ibm-thinks-ready-turn-quantum-050100574.html
OpenSuperQ Updated 2025-07-16
OpenSuperQ intro by Quantum Flagship (2021)
Source. Oxford Quantum Circuits Updated 2025-07-16
Their main innovation seems to be their 3D design which they call "Coaxmon".
Funding:
- 2023: $1m (869,000 pounds) for Japan expansion: www.uktech.news/deep-tech/oqc-funding-japan-20230203
- 2022: $47m (38M pounds) techcrunch.com/2022/07/04/uks-oxford-quantum-circuits-snaps-up-47m-for-quantum-computing-as-a-service/
- 2017: $2.7m globalventuring.com/university/oxford-quantum-calculates-2-7m/
The Coaxmon by Oxford Quantum Circuits (2022)
Source. There are unlisted articles, also show them or only show them.