Mark Mitchison
@mitchison.bsky.social
Theory of Controlled Quantum Systems | @royalsociety.org University Research Fellow @ King’s College London | Editor @quantum-journal.bsky.social & New Journal of Physics | He/him | posts ≈ 60% science/30% politics/11% nonsense
Reposted by Mark Mitchison
2025 Headline of the Year nominee (July)
December 22, 2025 at 11:53 PM
2025 Headline of the Year nominee (July)
Reposted by Mark Mitchison
Enough of this finite initial segment nonsense. A number is even if there is no remainder when divided by 2. \Aleph_0 = 2 \Aleph_0, so by cardinality, there is an even number of naturals *and* an even number of integers. And even if there was one more, that would still be an even number!
December 17, 2025 at 12:33 AM
Enough of this finite initial segment nonsense. A number is even if there is no remainder when divided by 2. \Aleph_0 = 2 \Aleph_0, so by cardinality, there is an even number of naturals *and* an even number of integers. And even if there was one more, that would still be an even number!
Here’s the whole crew at the film’s world premiere at AMBER research centre last week 🥰
November 17, 2025 at 8:23 AM
Here’s the whole crew at the film’s world premiere at AMBER research centre last week 🥰
We cooked up the idea for this experiment over a very fine dinner at our first full @aspects-quantum.bsky.social consortium meeting in Murcia, almost 2.5 years ago. Just shows the importance of good company, free conversation, and some good food 🥘🧁 and wine 🍷 for the scientific and creative process!
November 16, 2025 at 5:06 PM
We cooked up the idea for this experiment over a very fine dinner at our first full @aspects-quantum.bsky.social consortium meeting in Murcia, almost 2.5 years ago. Just shows the importance of good company, free conversation, and some good food 🥘🧁 and wine 🍷 for the scientific and creative process!
Huge thanks to @aspects-quantum.bsky.social partners @naresgroup.bsky.social @quitphysics.info and especially Vivek Wadhia and @mathsmire.bsky.social who really pushed this project from its conception to completion. It’s wonderful to see it all finally come to fruition. ❤️
November 16, 2025 at 5:06 PM
Huge thanks to @aspects-quantum.bsky.social partners @naresgroup.bsky.social @quitphysics.info and especially Vivek Wadhia and @mathsmire.bsky.social who really pushed this project from its conception to completion. It’s wonderful to see it all finally come to fruition. ❤️
An interesting implication is that, to make timekeeping efficient in the quantum domain, we should try to avoid measuring the ticks! It’s better to couple the clock directly to whatever system it needs to regulate.
November 16, 2025 at 5:06 PM
An interesting implication is that, to make timekeeping efficient in the quantum domain, we should try to avoid measuring the ticks! It’s better to couple the clock directly to whatever system it needs to regulate.
They showed that, for a quantum clock, the entropic cost of recording the ticks dominates the cost of generating them by many orders of magnitude. This not only resolves the paradox of “equilibrium clocks”, but also holds true in the optimal case where the clockwork itself is far from equilibrium
The Costs of Quantum Timekeeping
Experiments reveal the surprisingly large amount of entropy—and thus heat—generated by a clock that could be part of a quantum processor.
physics.aps.org
November 16, 2025 at 5:06 PM
They showed that, for a quantum clock, the entropic cost of recording the ticks dominates the cost of generating them by many orders of magnitude. This not only resolves the paradox of “equilibrium clocks”, but also holds true in the optimal case where the clockwork itself is far from equilibrium
But can a clock—which distinguishes past from future—be truly reversible? Of course not! The resolution is that monitoring equilibrium fluctuations requires a detector that is out of equilibrium, producing entropy. Our friends @naresgroup.bsky.social showed this in a proof-of-principle experiment.
November 16, 2025 at 5:06 PM
But can a clock—which distinguishes past from future—be truly reversible? Of course not! The resolution is that monitoring equilibrium fluctuations requires a detector that is out of equilibrium, producing entropy. Our friends @naresgroup.bsky.social showed this in a proof-of-principle experiment.
This reflects a general feature of stochastic clocks, as my colleagues and I showed here doi.org/10.1103/rpls...
The optimal observable to estimate time is time-reversal symmetric: it doesn’t care about the direction of time’s arrow, only its length
www.newscientist.com/article/2439...
The optimal observable to estimate time is time-reversal symmetric: it doesn’t care about the direction of time’s arrow, only its length
www.newscientist.com/article/2439...
You can turn any random sequence of events into a clock
A set of mathematical equations can help turn apparently random observations into a clock – and then measure its accuracy
www.newscientist.com
November 16, 2025 at 5:06 PM
This reflects a general feature of stochastic clocks, as my colleagues and I showed here doi.org/10.1103/rpls...
The optimal observable to estimate time is time-reversal symmetric: it doesn’t care about the direction of time’s arrow, only its length
www.newscientist.com/article/2439...
The optimal observable to estimate time is time-reversal symmetric: it doesn’t care about the direction of time’s arrow, only its length
www.newscientist.com/article/2439...