Jonathan Oppenheim
@postquantum.bsky.social
Quantum mechanic with a lot of ontological baggage.
https://www.ucl.ac.uk/oppenheim/
https://www.ucl.ac.uk/oppenheim/
Another day, another arxiv paper claiming that classical gravity can produce entanglement. Last week's Nature paper continues to cause confusion. But classical fields can't create entanglement *even if* they directly couple two masses. Comment added at superposer.substack.com/p/no-classic...
October 28, 2025 at 3:24 PM
Another day, another arxiv paper claiming that classical gravity can produce entanglement. Last week's Nature paper continues to cause confusion. But classical fields can't create entanglement *even if* they directly couple two masses. Comment added at superposer.substack.com/p/no-classic...
Maite Arcos's PhD results are hitting the arxiv! A resource theory of gambling, and a paper on adversarial thermodynamics are out today. Gambling provides an operational way to quantify who has more information. And it can be extended into the quantum domain!🧵🧪⚛️ 1/
October 10, 2025 at 7:15 AM
Maite Arcos's PhD results are hitting the arxiv! A resource theory of gambling, and a paper on adversarial thermodynamics are out today. Gambling provides an operational way to quantify who has more information. And it can be extended into the quantum domain!🧵🧪⚛️ 1/
They sure take electromagnetism seriously in @quantumaephraim.bsky.social's lab!
September 25, 2025 at 5:35 PM
They sure take electromagnetism seriously in @quantumaephraim.bsky.social's lab!
I'm at the African Institute for Mathematical Science Ghana this week for a quantum hackathon. Which is apparently called a Quantathon! Excited to interact with great students and researchers from across Africa. Live feed at t.co/J8UzPKc6Vx & schedule at qtedu.aims.edu.gh. Public lecture on Friday.
July 8, 2025 at 12:26 PM
I'm at the African Institute for Mathematical Science Ghana this week for a quantum hackathon. Which is apparently called a Quantathon! Excited to interact with great students and researchers from across Africa. Live feed at t.co/J8UzPKc6Vx & schedule at qtedu.aims.edu.gh. Public lecture on Friday.
and (apparently) the multiverse.
April 24, 2025 at 4:42 PM
and (apparently) the multiverse.
And merging black holes (Ringdown by Conrad Shawcross)
April 24, 2025 at 4:40 PM
And merging black holes (Ringdown by Conrad Shawcross)
I'm at the Quantum Symposium at @uniofnottingham.bsky.social and they have a working Lego interferometer!
April 24, 2025 at 4:40 PM
I'm at the Quantum Symposium at @uniofnottingham.bsky.social and they have a working Lego interferometer!
If we want fewer psychopaths in charge, we should start with ranked-choice voting. It’s about as complicated as picking pizza toppings with friends.
April 21, 2025 at 9:05 AM
If we want fewer psychopaths in charge, we should start with ranked-choice voting. It’s about as complicated as picking pizza toppings with friends.
The final session, on "Table-top quantum experiments for gravity" with Flaminia Giacomini, Richard Howl and Sougato Bose, closes out the QISS conference in Vienna vienna2025.qiss.fr/index.html. The recorded talks and subsequent discussion should appear online in the coming days. 🧪⚛️
April 17, 2025 at 2:09 PM
The final session, on "Table-top quantum experiments for gravity" with Flaminia Giacomini, Richard Howl and Sougato Bose, closes out the QISS conference in Vienna vienna2025.qiss.fr/index.html. The recorded talks and subsequent discussion should appear online in the coming days. 🧪⚛️
Tim Gowers @wtgowers.bsky.social claimed that Grok solved the Dubnový Blázen problem as an April Fools Day joke. Now Google thinks the Dubnový Blázen problem is a real problem in graph theory (it's Czech for "April Fools").
April 4, 2025 at 4:00 PM
Tim Gowers @wtgowers.bsky.social claimed that Grok solved the Dubnový Blázen problem as an April Fools Day joke. Now Google thinks the Dubnový Blázen problem is a real problem in graph theory (it's Czech for "April Fools").
This is part of DESI's recently released map of our universe. Each snowflake in this blizzard is a galaxy. Not sure if it's terrifying or comforting, but it's definitely jawdropping! More videos at noirlab.edu/public/video... 🌌⚛️ 🧪
March 20, 2025 at 10:56 PM
This is part of DESI's recently released map of our universe. Each snowflake in this blizzard is a galaxy. Not sure if it's terrifying or comforting, but it's definitely jawdropping! More videos at noirlab.edu/public/video... 🌌⚛️ 🧪
It wasn't long ago that @hossenfelder.bsky.social famously critical of new physics theories, highlighted the postquantum theory of gravity as one of the top five breakthroughs of 2024. But is the honeymoon over? ⚛️ 🧪1/
March 12, 2025 at 2:59 PM
It wasn't long ago that @hossenfelder.bsky.social famously critical of new physics theories, highlighted the postquantum theory of gravity as one of the top five breakthroughs of 2024. But is the honeymoon over? ⚛️ 🧪1/
The paper vs the press release 9/
February 21, 2025 at 11:06 AM
The paper vs the press release 9/
There, you can find the mathematically consistent way to couple classical spacetimes to quantum fields via a trajectories approach, which results in the behaviour shown here because it accounts for correlations between matter and spacetime (unlike the semi-classical equations) 5/
December 18, 2024 at 1:43 PM
There, you can find the mathematically consistent way to couple classical spacetimes to quantum fields via a trajectories approach, which results in the behaviour shown here because it accounts for correlations between matter and spacetime (unlike the semi-classical equations) 5/
If treated as fundamental, these theories are mathematically inconsistent. The expectation value of the stress-energy tensor of a planet in superposition is the same as two half planets, so the semi-classical Eqns G=8π<T> make no sense 3/
December 18, 2024 at 1:43 PM
If treated as fundamental, these theories are mathematically inconsistent. The expectation value of the stress-energy tensor of a planet in superposition is the same as two half planets, so the semi-classical Eqns G=8π<T> make no sense 3/
I'm in Vienna, discussing experimental tests of the quantum nature of spacetime. Markus Arndt and Stefan Gerlich perform interference experiments using heavy macromolecules which can test the quantum nature of spacetime via the "decoherence-vs-diffusion trade-off" www.nature.com/articles/s41... 🧪⚛️
November 27, 2024 at 2:19 PM
I'm in Vienna, discussing experimental tests of the quantum nature of spacetime. Markus Arndt and Stefan Gerlich perform interference experiments using heavy macromolecules which can test the quantum nature of spacetime via the "decoherence-vs-diffusion trade-off" www.nature.com/articles/s41... 🧪⚛️
What @rose.bsky.team clarifies is that this freedom is merely an intended feature, and doesn't exist at the moment. I take them at their word that they intend to grant us the freedom to leave -- by all accounts they are wonderful humans. But each day that passes makes this freedom less likely. 2/
November 20, 2024 at 9:44 AM
What @rose.bsky.team clarifies is that this freedom is merely an intended feature, and doesn't exist at the moment. I take them at their word that they intend to grant us the freedom to leave -- by all accounts they are wonderful humans. But each day that passes makes this freedom less likely. 2/
On my way to Amsterdam to give a talk at the BrainWash festival brainwashfestival.nl/en/festival/ and will later take the sleeper train to Vienna where I'll spend November discussing experiments to test the (post)quantum nature of spacetime. See some of you there?!
October 25, 2024 at 12:15 PM
On my way to Amsterdam to give a talk at the BrainWash festival brainwashfestival.nl/en/festival/ and will later take the sleeper train to Vienna where I'll spend November discussing experiments to test the (post)quantum nature of spacetime. See some of you there?!
Physics question: how would you shorten the period of this harmonic oscillator?
October 16, 2024 at 11:17 AM
Physics question: how would you shorten the period of this harmonic oscillator?
Here is the path integral for Brownian motion straight out of Feynman and Hibbs. It has higher derivatives, but just describes a free particle being hit by random forces. On average the acceleration (q double dot) is zero, but there are contributions away from this. 4/
![The path integral for Brownian motion (action \ddot{q]), vs the quantum path integral. The Brownian motion path integral doesn't have ghosts!](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:uknpj5mh4cfutreceecdbv7x/bafkreiaxmgp3zs56mwwliqllaoapgjua2dols47rlny2dw7ty36tlq7nkm@jpeg)
September 17, 2024 at 1:56 PM
Here is the path integral for Brownian motion straight out of Feynman and Hibbs. It has higher derivatives, but just describes a free particle being hit by random forces. On average the acceleration (q double dot) is zero, but there are contributions away from this. 4/
(i) Gravity is not a force, because it can be described by a universal geometry in which all other fields live. In this sense, gravity is unique. This is the equivalence principle. Test particles just free fall, and so no force is acting upon them. 2/
September 12, 2024 at 11:19 AM
(i) Gravity is not a force, because it can be described by a universal geometry in which all other fields live. In this sense, gravity is unique. This is the equivalence principle. Test particles just free fall, and so no force is acting upon them. 2/
This means it has the potential to reproduce phenomenology such as structure formation, lensing, and galactic rotation curves. For example, in the bullet cluster, light rays bend in such a way to reveal the appearance of dark matter, while the visible matter is elsewhere. 3/
July 23, 2024 at 2:14 PM
This means it has the potential to reproduce phenomenology such as structure formation, lensing, and galactic rotation curves. For example, in the bullet cluster, light rays bend in such a way to reveal the appearance of dark matter, while the visible matter is elsewhere. 3/
Neil Turok kicks off Cosmological Frontiers with a challenge calling for radical ideas. You can watch via zoom and the talks will be recorded at indico.ph.ed.ac.uk/event/277/time…. Tomorrow, I'll give an overview of recent progress in postquantum classical gravity. 1/
April 19, 2024 at 10:23 AM
Neil Turok kicks off Cosmological Frontiers with a challenge calling for radical ideas. You can watch via zoom and the talks will be recorded at indico.ph.ed.ac.uk/event/277/time…. Tomorrow, I'll give an overview of recent progress in postquantum classical gravity. 1/
Umesh Vazarani kicks off the "Quantum Complexity: Quantum PCP, Area Laws, and Quantum Gravity" workshop. Talks will be recorded and available here simons.berkeley.edu/workshops/qu.... I'll be around all week, come say hi!
March 18, 2024 at 4:45 PM
Umesh Vazarani kicks off the "Quantum Complexity: Quantum PCP, Area Laws, and Quantum Gravity" workshop. Talks will be recorded and available here simons.berkeley.edu/workshops/qu.... I'll be around all week, come say hi!