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steph

@gayladygrey.bsky.social

they/them or she/her; '96; theoretical quantum physicist; queer; nd; uk.

11 Posts72 Follower206 Folgt
steph@gayladygrey.bsky.social · 7mo ago

Lazy Quantum Walks with Native Multiqubit Gates: Quantum walks (QWs) as a benchmark for effective multiqubit gate fidelities; via detailed realistic error modelling for neutral atom hardware we pinpoint the native multiqubit gate sweet spot for standard & lazy discrete QWs. arxiv.org/abs/2511.21608

"Figure 6: Final fidelity of the final position states between errorless and simulated error 1q-coin (circles) and 2q-coin (triangles) QWs on 2n-node rings, using native gate set G(max(r) = 3). Pink solid lines denote QWs on 4-node rings, dashed blue on 8-node rings, and dotted gold lines on 16-node rings. IBM results (using native gates of max(r) = 2) [15] for 1q-coin QWs are also shown for comparison in crosses." Figure shows that 1q-coin QW on 4-node ring has final state fidelity >0.9 for 21 steps; 2q-coin (lazy) QW on 4-node and 1q-coin QW on 8-node has fidelity >0.9 for 10 steps and >0.8 for 20 steps; 2q-coin QW on 8-node and 1q-coin QW on 16-node has >0.9 for 5 steps, >0.8 for 8 steps, and >0.5 for 21 steps; lastly 2q-coin QW on 16-node >0.9 for 2 steps, >0.8 for 4 steps, and >0.5 for 10 steps. In all cases this is a marked improved over IBM results."Figure 9: Mean increase in composite fidelity f (max(r)) = Product^{max(r)−1}_{k=2} F(CkZ)^{no. of CkZ} from using native gate set G(max(r)) compared to using gate set G(max(r) − 1), with the number of multiqubit gates required for one step of a 2q-coin QW on a 2^n-node ring, where n ∈ {6, 8, 10, 12} in blue dots, green crosses, gold pluses, and red circles respectively. Inset shows corresponding average composite fidelity." Figure shows f(max(r=3)) to f(max(r-4)) has average increase of 0.15, 0.15, 0.13, 0.09 for n ∈ {6, 8, 10, 12} respectively; f(max(r-1) to f(max(r)) for r ∈ {5,6,7} has average increase of <0.04 for each n. Inset shows average f over 3<=max(r)<=7 of 0.3<f<0.5, 0.4<f<0.6, 0.6<f<0.8, 0.7<f<0.9 for n ∈ {6, 8, 10, 12} respectively.
Zoltán Zimborás@zoltanzimboras.bsky.social · 2y ago

To reach some consensus about the prospects of near-term (late nisq and early fault tolerant) quantum computing, we had a 3-day discussion event (“Quantum Now”) in Lapland with both optimists and pessimists. This continued at SeeQA 2024 in Oxford. See our conclusions here arxiv.org/abs/2501.05694

Myths around quantum computation before full fault tolerance: What no-go theorems rule out and what they don't

In this perspective article, we revisit and critically evaluate prevailing viewpoints on the capabilities and limitations of near-term quantum computing and its potential transition toward fully fault...

arxiv.org

Stop the War Coalition@stwc.bsky.social · 2y ago

At least 150 MPs, Peers, civil society organisations and activists, trade union leaders, cultural figures, healthworkers and many more have signed a statement condemning police barring 18 January march from the BBC. Full list here 🔽 stopwar.org.uk/article/stat... #WeWillMarch

Statement on police barring 18 January march at the BBC

The right to free speech is precious. We call on the police to drop their objections and allow the protest to go...

stopwar.org.uk

steph@gayladygrey.bsky.social · 2y ago

Newly published paper on generalizing concentratable entanglement (CE) and the c-SWAP test to mixed and higher dimensional states! We define an upper bound of CE, propose a c-SWAP test on optical states, and characterize entangled coherent states' CE. royalsocietypublishing.org/doi/10.1098/...

Generalizing multipartite concentratable entanglement for practical applications: mixed, qudit and optical states | Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engine...

The controlled SWAP test for detecting and quantifying entanglement applied to pure qubit states is robust to small errors in the states and efficient for large multi-qubit states (Foulds et al. 2021 ...

royalsocietypublishing.org

Daniel Litt@littmath.bsky.social · 2y ago

I just sat down in a chair, and was supported because of trillions of quantum-mechanical interactions between the particles in my butt and the particles in the seat. This lends credence to the notion that quantum computation occurs in many parallel universes, an idea first propo

ditchpony@ditchpony.bsky.social · 2y ago

I’m only a failure by human standards. if I was a children’s book badger in an apron I’d be like “whoa this house is massive, and I own so many cheeses and jams.”