iiinova — where your digital self keeps evolving

Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 31/07/2026

We find, surprisingly, that the model mapping to two-level disorder wasn't enough to produce a true localised phase – in fact, we thermalise fairly quickly following a quench! Whereas for n = 4, 8 we see long-lived localisation and other signatures of a localised phase (like "area law" entanglement)

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 31/07/2026

New paper! arxiv.org/abs/2607.26156 ⚛️🧪 We study disorder-free localisation (DFL) - an intriguing phenomenon where dynamical degrees of freedom become localised and frozen, in the absence of the strong disorder (such as a random on-site magnetic field) normally needed to induce this effect. 🧵

Figure 1. (a) Schematic of a Z2 lattice gauge theory and its mapping to an effective spin chain with n-level bond disorder.
Top: Z2 gauge fields coupled to matter, with static external “flavor” particles coupled to the matter. Middle: After gauge fixing
and eliminating matter fields (see Appendix A), the model maps to a mixed-field Ising chain with disordered couplings gj , whose
signs and magnitudes are set by the occupations of the flavor particles. Bottom: Introducing n-level ancilla
Sj+1/2 renders
the model translationally invariant, enabling efficient disorder averaging (see Sec. V). (b) Each n-level ancilla requires log2(n)
qubits, with consequences for experimental simulation of disordered models. (c) Schematic summary of the phase diagrams
obtained in this work as a function of longitudinal field h and coupling µ. For n = 2 the system remains chaotic throughout
with slow dynamics at large h, while for n>2 localized and fragmented regimes emerge at large µ and h respectively.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 14/05/2026

I've seen some great "University of Nothingham" signs/posters about

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 12/05/2026

We were able to study the transport of both fermions and hard-core bosons, measuring the currents through the system, and seeing how these responded to turning on a magnetic field or interactions between particles. Below, we see that turning on the magnetic field (b) pushes currents to the edge!

(a) Final snapshots for the local density and instantaneous currents measured on the H1-1 device for fermions with V = 0,ϕ = 0 (m = 14 timesteps, ∆t = 0.21), and (b) for V = 0,ϕ= π/2 (m = 16 timesteps, ∆t = 0.27). Both snapshots were averaged over 1480 trajectories.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 12/05/2026

New paper from our group today! arxiv.org/abs/2605.08350 Using a quantum computer, we simulated trajectories of an open quantum system - that is, one that interacts with the surrounding environment, in this case by injecting particles at one end of a 2D lattice and removing them from the other. ⚛️🧪

FIG. 1. (a) The setup consists of a 4 × 4 square lattice with nearest neighbour hopping (directed arrows) and interactions (dashed line). Stochastic driving acts on the two corner sites labelled “source” (red) and “drain” (blue) with probability p.

(b) Schematic of the quantum trajectory realised by our driving scheme, showing the local density on the source (top) and the total particle number (bottom). The black line is a single trajectory, with source and drain jumps indicated by dashed lines, and grey line indicates the average.

(c) The corresponding circuit starts with unitary state preparation followed by unitary evolution using a Trotter decomposition. The non-unitary step uses an ancilla qubit for a “quantum coin flip” with probability p that classically conditions a measurement and reset on the source and drain. After m timesteps of the unitary and non-unitary drive we perform a full-circuit measurement to extract observables such as local densities and currents

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 05/04/2026

We were decorating hot cross buns today so I attempted to make a quantum physics one…I’ll have to work on my icing skills 😅

A brown, rounded bun with icing on it. The icing reads, in terrible handwriting, Hψ = i dψ/dt

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 20/03/2026

Watched the new Spiderman trailer, why is *this* the moment I’m excited by? 😅 (No, not Bruce Banner, what’s behind him!)

A still from the new Spider-Man trailer. It shows Bruce Banner (played by Mark Ruffalo) standing in front of a presentation slide on “Lattice Quantum Chromodynamics (QCD)”, although he’s standing in the way of most of it

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 02/11/2025

I’ve always thought the problem with quantum computers is that they don’t cost nearly enough money (ideally, at least a million dollars per kg!), and should experience heavy vibrations and crushing G-forces after being calibrated. ⚛️🧪

E*** M*** on X, The Everything App:

“Quantum computing is best done in the permanently shadowed craters on the Moon”

107,000 idiots have liked this Xeet.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 26/09/2025

Just finished the final day of the Nottingham Workshop on Quantum Non-Equilibrium Dynamics!! Lots of great talks, and great discussions too 😄

A photo of one of the talks. People are sitting in chairs watching someone present a talk, specifically Mark Mitchison (KCL) on the topic of process tensors.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 10/09/2025

The British Isles, according to the New York Times. (I think some of my old colleagues from Leeds might have an aneurysm if they see this!)

A screenshot from a New York Times article:

"I have great sympathy for the police," said Paul Wragg, a professor of media law at the University of Leeds, north of London. He said that the public would likely be…”

An outline map of the British Isles. London is labelled, and every other part is labelled relative to London: for example, Wales is “West of London”, Scotland is “far north of London”, and Ireland is “Far west of London”

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 21/07/2025

Pros of showing up to an anti-cuts rally: • Stand in solidarity with colleagues • Protect your university from shredding its reputation • Defend research and innovation • This cute little dog who barked (loudly!) every time people clapped 🥰 #AcademicChatter

A small black and brown dog in the middle of barking, nestled between someone’s legs. There are some people standing around the white-tiled courtyard although you can’t see their faces. One of them is holding a purple and green Unison flag

A wide angle shot of the same courtyard. Many people are standing around, waving flags and banners from different unions. In the background someone is giving a speech

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 31/05/2025

Hey! I have a website now 👨🏻‍💻 jaredjeya.github.io Still a WIP as I’m figuring out how it all works and what to put on it, though (I used a slightly over-engineered template 😅). Also if anyone knows how to make images show up in the link card, that would be cool!

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 19/05/2025

Ok here’s my attempt to come up with time travel in this scenario. Let’s assume that the “shortcut” works in any reference frame (otherwise that breaks the equivalence principle). Consider this spacetime diagram:

A spacetime diagram described in the next tweet

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 15/04/2025

Poster session at QuSymDyn, Munich! Come speak to me if you want to know more about disorder-free localisation in the Schwinger model :)

A poster on “Hilbert space fragmentation at the origin of disorder-free localisation in the lattice Schwinger model”, showing a number of graphs, equations and diagrams

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 14/03/2025

Happy pi(zza) day! (Although I prefer to celebrate on 22/7 - it’s a lot more accurate 😉) #PiDay

A delicious chorizo & ham pizza, in a brown pizza box. It’s sitting on a dark wooden table in a pub. A half-drunk pint of stout is also visible!

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 10/12/2024

Loving the barely-restrained disdain for the marketing hype exhibited by Dr Leek here #QuantumComputing #physics www.theguardian.com/technology/2...

“Quantum processors are peeling away at a double exponential rate and will continue to vastly outperform classical computers as we scale up,” said Hartmut Neven, the founder of the firm, who said that the latest test results, published on Monday in Nature magazine, “cracks a key challenge in quantum error correction that the field has pursued for almost 30 years”.

He said the far greater speed of the new chip than classical computers “lends credence to the notion that quantum computation occurs in many parallel universes, in line with the idea that we live in a multiverse”.

Simply put, if a quantum computer can be in many different states at once, it can get more done at the same time.

Dr Peter Leek, research fellow at the University of Oxford’s Quantum Institute and founder of Oxford Quantum Circuits, said: “It’s definitely thought-provoking to put it that way. What it really does is show that quantum computing technology is rapidly moving forward. It really is working.”

He described the Google results as a “shining example” of improvements in error correction, but he cautioned that the very fast processing results related to calculations that were “not of much real-world use”.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 23/11/2024

These were obtained using the time-dependent variational principle - this is a method that projects quantum dynamics onto a variational manifold, so you effectively get a semi-classical approximation within which you can observe *classical* chaos etc! (I’ve put some more info in the alt text)

An illustration of TDVP. We consider a state in some variational manifold (black-bordered surface). The state ψ (red dot) will evolve under the full dynamics in the direction of -iHψ, however as we constrain ourselves to the manifold we project this down into the tangent space (blue plane) to the manifold at that point. This gives an optimal approximation to the full dynamics within the manifold. Over time, the state will move through the manifold (green line).

This is also equivalent to the saddle-point approximation of the dynamics in the manifold, which is one way we can consider this to be a sort of semi-classical approximation.

Image source: https://arxiv.org/abs/1807.01815

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 22/11/2024

Who says that physics can’t also be art? This was shared by a colleague in a seminar this morning - see if you can guess what it depicts! 🧪⚛️ #physics #quantum #SciArt

A section of a highly colourful plot, made up of many small coloured dots. In various spots, dense & regular concentric circles of different colours can be seen, surrounded by regions which appear more chaotic with many dots of different colours interleaving. Smaller circular (and less circular) regions can also be seen in between the larger ones, as well as on the edges of the large rings. The white background is barely visible.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 05/11/2024

Share your mug! (I love conferences that give out free mugs)

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 01/11/2024

If you see this, post a photo taken in the mountains

The view from the top of a multipitch climb in El Chorro, Spain. In the foreground, a rocky mountainside is visible, and in the background are green forested hills

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 29/09/2024

A real diagram from a real paper I’m reading right now! #physics #AcademicChatter

A diagram featuring three drawings of turtles and an arrow labelling increasing “coupling K”. They get progressively more detailed (from outline sketch to coloured in + shaded) as K increases.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 24/09/2024

I’m now officially a contributor to python’s numba package 🤓

A screenshot of a commit to numba, merging my pull request.

“Merge pull request #9338 from jaredjeya/add-setops1d”

“Add np.in1d, np.isin, np.setxor1d,
пр.setdiff1d, extend np.intersect1d”

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 22/09/2024

Messing about with iOS’s new Maths Notes feature and apparently it’s fairly easy to completely lock up the app 😅 #maths #iOS18

A screenshot of the iOS notes app, with three equations: “y = x”, “y = x*x -3”, and “y = sin(e^x” [sic - I couldn’t type the closing bracket!]

Below is a graph faithfully rendering these three equations. The final line starts at zero on the left and, on approaching the x axis in the centre, starts to oscillate, rapidly becoming a solid mass between -1 and 1.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 21/09/2024

Post a butterfly to celebrate 10 million users on Bluesky! 🦋 This is Hofstadter’s Butterfly, a fractal that emerges from plotting the energy spectrum of a charged particle moving in a square lattice in the presence of a magnetic field. Quantum physics can be beautiful too! #physics 🧪 ⚛️

$Hofstadter’s Butterfly. Four lines meet at a point in the middle, and these then break apart into fractal structures as you move away from the centre. There’s a beautiful symmetry to the whole picture.$ Experimental verification of the butterfly. It looks a lot more like a butterfly than the theoretical picture! You can see four wing-like lobes branching off from the centre.

Experimental verification of the butterfly. It looks a lot more like a butterfly than the theoretical picture! You can see four wing-like lobes branching off from the centre.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 17/09/2024

At the Localisation conference at MPI Dresden - posters are up! 🧪⚛️ #physics #locali24

A poster based on our recent paper - Hilbert space fragmentation at the origin of disorder-free localization in the lattice Schwinger model

Click the link in my bio to find it!

A poster based on my paper “Renormalization view on resonance proliferation between many-body localized phases” - check the link in my bio to read it!

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 17/09/2024

What does this all mean? Our results suggest apparent signatures of a many-body localised (MBL) phase can be accounted for by a single phase deriving from the observed fragmentation in the infinite-coupling limit, rather than the mechanisms of conventional disorder-driven MBL (6/7)

Schematic phase diagram for the 1D lattice
Schwinger model as a function of the dimensionless coupling
ratio J/w. In the weak-coupling limit
J/w → 0, the model reduces to an integrable XY spin chain.
In the thermodynamic limit, any finite J breaks integrability,
resulting in a chaotic phase. Around J/w ∼ 1, an ergodicity breaking transition, consistent with an onset of MBL, has previously been observed. However, the nature and extent of
MBL phase is difficult to ascertain in finite-size systems due to
its proximity to the regime dominated by Hilbert space fragmentation. The latter is exact at J/w → ∞ and, as shown
in this paper, strongly affects the properties of numerically accessible systems even at J/w ∼ 10.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 17/09/2024

We find that the claimed ultra-slow entanglement growth results from this fragmentation, and show (including with matrix product state simulations) that is more naturally explained by a single-log at short times with a slow power-law relaxation to a finite-size saturation value at late times: (5/7)

Growth of entanglement entropy from the |vac⟩ initial state for system size N = 50 at J/w = 3, obtained via MPS simulations (see Methods for details). The data is averaged over 600 background charge sectors, with the standard deviation represented by the shading. The dashed lines indicate different types of fits summarized in the legend. In the
inset, we show the same data on a log-log scale.

Sector-averaged configurational entropy, S_C(t), for J = 8 and system sizes N = 8, 10, 12, 14, 16 (solid lines). For each N we fit a power-law of the form S_C(t) = S_∞ − S_0 t^(−α) (dotted lines). In the inset, we show the power-law decay towards the fitted saturation value, ∆S_C = S_∞ − S_C (t) for N ≥ 10.

We find the power-law exponent seems to tend towards 0 with increasing N and J, suggesting that this might be going towards a standard log law - or alternatively, that we can no longer access the saturation regime with finite time numerics.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 17/09/2024

Inspecting this model more closely, we find that in the strong-coupling limit, spin exchange is only allowed when the forces due to dynamical particles and background charges balance out. This leads to frozen dynamics in parts of the chain, and fragmentation of the phase space! (4/7)

(a) The parity P over some region gives the total charge in the original gauge theory; this must sum to zero over the whole chain.

(b) Exchanging |10⟩ ↔ |01⟩ at sites 2ℓ and 2ℓ + 1 creates an e−e+ pair. This is resonant if the gauge field L_2ℓ = 0, i.e. if the fermionic and background charges sum to zero.

(c) For a particular charge sector and spin configuration, only certain bonds satisfy the previous condition and thus permit dynamics in the large-J limit. These “active regions” are independent and so the effective Hamiltonian is a sum of local commuting terms.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 17/09/2024

In particular, there have been claims of *disorder-free localization*: one finds emergent background charges which lead to an effective disorder ensemble, localising particles and leading to a claimed ultra-slow growth of entanglement. See e.g., journals.aps.org/prl/pdf/10.1... (3/7)

From Brenes, Dalmonte, Heyl, and Scardicchio, "Many-Body Localization Dynamics from Gauge Invariance", PRL 120, 030601 (2018):

(c) Long-time growth of S_A(t) for J = 10 including a fit (solid
line) f(t) a log[log(wt) + b to the N = 14 data. (d) The same
data are plotted on a double logarithmic scale.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 17/09/2024

This model we study is a model of quantum electrodynamics (think electrons and electromagnetic fields) in 1D, defined on a discrete lattice. Originally developed to help understand their continuous cousins, models like these have become a rich source of novel physics in their own right. (2/7)

The 1D lattice Schwinger model (top) describes quantum electrodynamics on a lattice.
Fermionic degrees of freedom ψ_n on odd (even) sites represent the presence or absence of an electron (positron), while the electric fields L_n reside on the bonds and mediate coupling between the particles. In 1D, one can integrate out the fields and apply a Jordan-Wigner transform, which results in a an XY-type model for spins σ =↑, ↓. The dynamical fields are replaced by static background charges q_n, which act as a disorder potential for spins.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 11/09/2024

When my PI asks me to explain my new research idea:

Donald Trump at the debate saying, “I have concepts of a plan”

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 03/09/2024

Yesterday, only a whole nine months after passing my viva (thanks UCL 😅), I finally graduated! Massive thanks to my parents, my PhD supervisor Arijeet Pal, and all my colleagues for their support 😊 #AcademicChatter

My parents!

Description: Jared, grinning, in a grey and red PhD gown and wearing a black academic cap (not a mortarboard! but a round, baggy hat with a hard wide brim). He’s flanked by his parents.

My PhD supervisor!

Description: Jared, in a grey and red gown and holding his thesis. He’s standing with his supervisor Arijeet in front of the UCL main building.

My colleagues! At least the ones who were in town 😂

Description: Jared, in a grey and red gown and holding his thesis. He’s standing with his supervisor Arijeet as well as some former colleagues in front of the UCL main building.

And that iconic photo opportunity had to be taken

Description: Jared and the same colleagues from the other photo, perched on a plinth in front of the UCL main building. The famous “portico” with stone columns is visible, looking like the prototypical classical building (it’s literally the emoji: 🏛️)

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 24/06/2024

Saw this poster at the Quantum Many Body Chaos conference. All these years wasted when I could have been studying Quantum Wiggliness! ⚛️ 🧪 (Here’s the paper if you want to know more, it looks pretty interesting: journals.aps.org/pre/pdf/10.1...)

A picture of a research poster with a red & blue colour plot in the centre. A caption reads “Wiggliness of OTOCs in energy eigenstates averaged over near levels in the spectrum” and an arrow points out “wiggliness suppressed by chaos”

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 17/06/2024

They can be good for sprucing up a laptop too! See if you can spot the ones on here (unfortunately none of them are Canadian - yet!)

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 11/05/2024

I seriously cannot believe that I just saw the Aurora Borealis in the middle of Leeds. All I did was walk to a nearby park and point my phone at the sky. It probably helps that solar activity is crazy high right now! ⚛️🧪

Aurora Borealis: beautiful purple and green hues in bands, with silhouettes of trees and fencing in the foreground.

Ditto but with more green and more distinct shapes

Back to purple and green. There are vertical lines visible, it almost looks like lens flare.

A graph showing that magnetic disturbance has hit 1350nT (for context, this app sends a “red alert” if it’s over 200nT).

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 01/04/2024

If I’d had night skies like these growing up, maybe I’d have become an astrophysicist instead! (Taken in Sossusvlei, Namibia, and the Okavango Delta, Botswana, respectively - with just an iPhone!)

An absolutely incredible night sky with the Milky Way clearly visible. (Unfortunately I’d find it hard to do it justice here - I’m not a poet!)

An absolutely incredible night sky with the Milky Way clearly visible. Some plants are silhouetted over the stars.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 04/03/2024

Tunisia is also full of cats! Had a lovely time there 😊

Two cats stretch out on a red brick pavement next to a wall; one is white and grey, the other beige.

A woman cradles a small and very cute black kitten in her arms while sitting down

A very sleepy brown and black cat lying on a doorstep in the shade

a very teeny white and brown kitten crouching on some stone tiles, looking toward the camera

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 28/02/2024

As long as it looks better than this I think you’re fine!

The worst plot you’ve ever seen. Multicoloured crosses are overlaid on multicoloured lines on top of density contours on top of triangles with error bars, with chunky histograms on the left and smooth ones on the bottom. There is text everywhere, some of it totally illegible, and a random colourbar. It keeps getting worse as you look more closely, with additional layers revealing themselves.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 22/02/2024

Oh dear. The DfT has fallen for quantum woo. (There are many things that would fix the UK train system, but handing it off to today’s quantum computers that can barely factorise the number 21 is not one of them.) #physics

Quantum supercomputer to tackle train delays in UK trial

Department for Transport to test algorithm designed to improve timetables and reduce disruption

James Titcomb
12 February 2024 • 1:21pm

A quantum supercomputer will be used to find ways to make Britain's trains run on time under tests from the Department for Transport aimed at overhauling rail schedules.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 10/02/2024

Hey Bluesky! Now that we’re open to the public, I thought I’d better reintroduce myself with a word cloud :) 🧪 ⚛️

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 26/01/2024

Slightly horrified that UCL didn’t change the filename before publishing my thesis! Could’ve been much worse than FINAL_THESIS.pdf 😅

A screenshot of the UCL thesis deposit website showing a download button labelled “FINAL_THESIS.pdf”.

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Dr Jared Jeyaretnam ⚛️🧪 @jaredjeya.github.io · 25/01/2024

TIL that climate criminals BP are on the cutting edge of quantum computing

A postcard for “Glentanglement, Scotland’s Quantum Valley”: a map of Scotland overlaid with a number of logos of quantum computing startups and universities, with the conspicuous addition of BP off to the side.

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