Exploring the physics of quantum matter in Cologne. Also at @SimonTrebst.bsky.social
Cologne, Germany
Joined February 2014
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🎬…and cut. We are done recording lectures for my “Computational Many-Body Physics” course.
Tune in if you want to break the exponential complexity of many-body systems with polynomial algorithms: Monte Carlo sampling, tensor networks & machine learning
vimeo.com/showcase/8290960
Simon Trebst retweeted
📢Join our vibrant international research environment to develop new #QuantumComputing and networking architectures! We offer 2-year #fellowships for excellent #postdocs.
Visit our website for more details: ml4q.de/ml4q-fellowships/ Don't miss the application deadline on March 12!
This is how the operation of a transmon gate looks like near the quantum speed limit — the dynamics turn chaotic and the system transitions out of the computational subspace. But does this mean that the gates are no longer operational?
Find out here:
arxiv.org/abs/2311.14592 – at Cologne, Germany
In quantum error correction, stabilizer codes using a set of *commuting* measurements (such as the toric code or surface code) have been the go-to solution for topological quantum memories — despite the need for multi-qubit measurements.
1/7 – at Berlin, Germany
ALT A schematic of the surface code, which requires 4-qubit measurements to implement the two commuting stabilizers that allow to encode two logical qubits in this kind of quantum memory.
So what’s inbetween the two peaks? A Majorana metal in which the entanglement negativity shows an L ln L scaling. Think of a long-range resonating valence bond state of the emergent Majoranas.
Preprint: arxiv.org/abs/2311.08450
6/7 – at Berlin, Germany
ALT Phase diagram of the Floquet honeycomb code as a function of measurement strength, shown here in terms of the ensuing Majorana states. https://arxiv.org/abs/2311.08450
Thanks to @GuoyiZhu for a fantastic collaboration pushing the limits of the Floquet code and exploring the physics beyond thresholds. – at Berlin, Germany
ALT Guo-Yi Zhu discussing the physics of the Floquet honeycomb code with weak measurements at the 2023 CRC 183 fall meeting in Berlin. https://www.crc183.uni-koeln.de
The Nishimori transition is a staple of stat mech — one of few exact results for the random-bond Ising model famous for its spin glass phase. Moving directly through the transition, however, is an exceedingly fine-tuned manoeuvre balancing thermal fluctuations and disorder.
1/3 – at Cologne, Germany
In contrast, Nishimori physics turns out to be a natural phenomenon in the *quantum* realm, guaranteed by no less than Born’s rule. This is how we could tune an actual 127 qubit device through this transition on the IBM quantum platform.
arxiv.org/abs/2309.02863
2/3 – at Cologne, Germany
ALT Experimental data showing the Nishimori transition traversed on ibm_sherbrooke, a 127-qubit device in IBM’s quantum cloud.
We also connect to seminal work by Dennis, Kitaev, Landahl, & @preskill on error thresholds & decoding — they established resilience against incoherent noise, while we discuss stability against coherent errors. Both limits are connected via a line of Nishimori transitions.
3/3 – at Cologne, Germany
Current-day quantum processors with 50-100 qubits already operate outside the range of what one can efficiently simulate on classical, silicon-based computers. So how do you design future generations of these processors that have even more qubits?
1/2
Turn your quantum processor into its classical regime — coupled, non-linear oscillators which might hover dangerously close to destabilizing chaotic resonances — and simulate its many-body physics. But does this really work?
Find out here:
arxiv.org/abs/2304.14435
2/2
A new class of *monitored* quantum circuits allows for unprecedented dynamical control of many-body entanglement. But how do you shape entanglement at will? Turns out this still needs a lot of back-and-forth on one of the most traditional devices — the blackboard.
1/3
Notably, one can create long-range, many-qubit entanglement bypassing any unitary evolution and using measurements only. We devise such a measurement-only circuit that gives rise to a *structured* volume-law entangled phase — a state of matter with no thermal counterpart.
2/3
Thanks @GuoyiZhu and @nat_tanti for plowing through this project over the past few weeks. Looking forward to shaping even more bizarre, non-equilibrium entangled states of matter.
arxiv.org/abs/2303.17627
3/3
Anyone interested in the power of classical versus quantum computing, should take time reading @MStoudenmire’s take on Grover’s algorithm today. Inspiring work!
In "Grover's Algorithm Offers No Quantum Advantage" we argue there is no a priori quantum speedup of Grover's algorithm over classical algorithms since a problem solvable by Grover's is structured: there must always be the structure of a quantum circuit.
arxiv.org/abs/2303.11317
Simon Trebst retweeted
Watch @SimonTrebst's Flatiron Seminar Series lecture on "Quantum Computing 'al dente'" on the @SimonsFdn site: simonsfoundation.org/event/f…
