Christopher K. Long

What happens to an electron if given quantized energy to jump to a full orbital? Let's consider the element neon. Its ground-state electron configuration is: $1s^2 2s^2 2p^6$. What would happen if enough energy was given for one electron in the $1s$ orbital to jump to the $2s$

For T1 you can use Fermi's Golden rule. Here is a post I made a few years ago for absorbing a photon:

physics.stackexchange.com/a/649933/305...

Keep the emission term instead. Also you will probably need more than minimal couping to the EM field to get the spin flip on emission.

PySTE now has pre-built wheels for Python 3.14!

That makes sense. I would be interested in the slides afterwards is Alex is happy to share them.

Do you know if the talk will be recorded? Unfortunately, I am teaching at this time.

py-ste A Python package for evolving unitaries and states under the Schrödinger equation using first-order Suzuki-Trotter and computing switching functions.

I guess it's time I release a 3.14 pre-built version of PySTE:
pypi.org/project/py-s...

What’s new in Python 3.14 Editors, Adam Turner and Hugo van Kemenade,. This article explains the new features in Python 3.14, compared to 3.13. Python 3.14 was released on 7 October 2025. For full details, see the changelog...

In case anyone else missed it: Python 3.14 released on the 7th of October:
docs.python.org/3.14/whatsne...

With a long transfer from the Sahara to Fes, I finally finished going through the starter packs below. It was great to see everything you all have been working on! I like to spend some time reading through each profile, so I start to remember who's working on what. Please comment more starter packs!

Well pip will not install a package that doesn't meet this requirement. Are you looking for tighter guarantees than that?

A screenshot of https://pypi.org/project/py-ste/#data showing the required Python version under Project Details > Unverified Details > Meta > Requires as `Python >=3.8`

If a Python package has a pyproject.toml you can look for the requires-python line:
`requires-python = ">=3.8"`. If you check the package on PyPI the requirements are also listed under Project Details > Unverified Details > Meta > Requires.

The European Commission is pleased to launch this new Science, Research & Innovation account. We look forward to connecting with the community on Bluesky! 🧪

Here you will find:
- EU scientific news
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Last academic year, I reviewed my first paper. To any other PhD student considering whether to accept or decline this opportunity: I found it insightful to be on the other side of the process. It will help me anticipate future reviewer questions and prepare responses.

I enjoy how ideas from maths, physics, and computing all meld. Then for quantum computation you can bring in an application subject such as chemistry or finance. The ability to draw ideas from so many fields makes me excited about my research! What is your favourite part?

I'm looking for more of these starter packs so thank you for putting it together! I would be grateful if you could add me too please :)

Figure 2 from: C. K. Long and C. H. W. Barnes, From virtual Z gates to virtual Z pulses, 2025. arXiv: 2509.13453 [quant-ph]. https://arxiv.org/abs/2509.13453. Caption: FIG. 2. Dilated pulses corresponding to virtual Z pulses. (Top row) The desired virtual Z pulses in units with ℏ = 1, with varying amplitudes: (left) derivative of Gaussian and (centre and right) derivative of hyperbolic tangent. The centre and right-hand columns differ only by the amplitude, with the right-hand column displaying larger amplitudes. (Second row from the top) The time-dilation required to implement the virtual Z pulse in the top row. The black curve in the centre column is an example of a virtual Z pulse that requires time compression. (Third row from the top) The distorted J pulse that implements a Gaussian (standard deviation 0.3) J pulse in the presence of the desired simultaneous virtual Z pulse. The purple curve corresponds to no virtual Z pulse—i.e., the undistorted pulse. (Bottom row) The distorted I′ (solid) and Q′ (dashed) pulses that implement a Gaussian (standard deviation 0.3) I pulse in the presence of the desired simultaneous virtual Z pulse—assuming the virtual Z pulse is applied only to qubit 1. Note that the J, I, and Q pulses can all be implemented simultaneously.

Example pulse distortions: (Top row) The modulation of a virtual Pauli-Z term in the system Hamiltonian. (2nd row) The time dilation required to implement the virtual Pauli-Z term without actually introducing it to the Hamiltonian. (3rd and 4th rows) The distorted two- and one-qubit control pulses.

From virtual Z gates to virtual Z pulses Virtual $Z$ gates have become integral for implementing fast, high-fidelity single-qubit operations. However, virtual $Z$ gates require that the system's two-qubit gates are microwave-activated or nor...

Ever wanted to use virtual Z gates with arbitrary powers of SWAP? Introducing the virtual Z pulse: arxiv.org/abs/2509.13453. In our new article, we present a method for distorting a pulse sequence to implement single-qubit Z controls virtually.

It is definitely a good thing to have opposing camps on the hypothesis. Whether it is true or not, as an outsider to the field, the idea caught my interest and allowed me to reminisce on some of my undergraduate Physics I don't use day to day.

This sent me down a fun rabbit hole learning about the rings Earth could have had—thank you!

I've been wondering why I haven't seen it in #quantum. I am looking into using it for my next preprints, but I am yet to start writing #lean. I have a few Lie algebraic proofs, and thought it would be nice to use #lean to ensure there are no mistakes.

The black solid curves represent numerically estimated cumulative probability distributions. The shaded region corresponds to a 99.99% confidence interval (CI) estimated via 105 bootstrap resamples (see “Methods” section). Vertical blue lines mark typical gate times. The dashed purple and orange curves are the homogeneous and isotropic (HI) fits and higher-order fits, respectively. For details on the fitting, see “Methods” section. Taken from: Long, C.K., Mayhall, N.J., Economou, S.E. et al. Minimal state-preparation times for silicon spin qubits. npj Quantum Inf 11, 113 (2025). https://doi.org/10.1038/s41534-025-01027-8 Under http://creativecommons.org/licenses/by/4.0/ No changes were made.

Even accounting for this, we find the effect persists: the separation of the black curve from the blue vertical line for (X±Y)/√2 increases with qubit number. We conjecture this is due to the use of the fast two-qubit operation to aid in implementing single-qubit operations in some entangled basis.

Second, we observe that the minimal evolution time decreases with the number of qubits in the system. This is partially an artefact of the fact that we have to split up our microwave antenna power between more frequency channels...

First, connectivity is not a limiting factor and should not be until we reach somewhere in the range of 10s–100s of qubits.

Thanks! We only performed numerics on 1–4 qubits with linear connectivity. For the device we modelled, the power of swap can be performed orders of magnitude faster than single qubit rotations. This leads to two interesting effects:

If you liked the preprint, then you should skim through the published version for all the new figures and data.

All data and code are publicly available:
doi.org/10.5281/zeno...
github.com/Christopher-...

This data could not have been collected without the libraries we developed for this project:

Curves show the probability of occupying the computational, valley, double-, triple-, and quadruple-occupation subspaces of a 4-site Hubbard model with valleys. The applied pulse achieves the ground-state of LiH at the equilibrium bound distance of 1.59 Å in the corresponding 4-spin Heisenberg model [21] within 20 ns. Taken from: Long, C.K., Mayhall, N.J., Economou, S.E. et al. Minimal state-preparation times for silicon spin qubits. npj Quantum Inf 11, 113 (2025). https://doi.org/10.1038/s41534-025-01027-8 Under http://creativecommons.org/licenses/by/4.0/ No changes were made. [21] Burkard, G., Ladd, T. D., Pan, A., Nichol, J. M. & Petta, J. R. Semiconductor spin qubits. Rev. Mod. Phys. 95, 025003 (2023).

Further, we consider random state transitions to bound the performance of arbitrary quantum algorithms. Finally, we study the robustness of the pulse-based approach to device imperfections and leakage:

(top) Molecular energy C(T) as a function of bond distance for a range of evolution times. At zero evolution time, C(0) corresponds to the (yellow) Hartree-Fock disassociation curve of the initial state. At the MET, the energy C(T = MET) (blue dissociation curve) converges to the full configuration interaction (FCI) energy C0 (dashed black curve). (bottom) Energy error Δ(T) := C(T) − C0 on a logarithmic color scale as a function of bond distance and evolution time. A white line shows the silicon METs. A dashed (gray) curve marks transmon METs [11]. Taken from: Long, C.K., Mayhall, N.J., Economou, S.E. et al. Minimal state-preparation times for silicon spin qubits. npj Quantum Inf 11, 113 (2025). https://doi.org/10.1038/s41534-025-01027-8 Under http://creativecommons.org/licenses/by/4.0/ No changes were made. [11] Meitei, O. R. et al. Gate-free state preparation for fast variational quantum eigensolver simulations. npj Quantum Inf. 7, 1–11 (2021).

Preparing molecular ground states for H₂, HeH⁺, and LiH in 2.3, 4.6, and 26.8 ns:

Minimal state-preparation times for silicon spin qubits - npj Quantum Information npj Quantum Information - Minimal state-preparation times for silicon spin qubits

How fast can quantum processors run? My coauthors and I answer in our new npj Quantum Information article! Utilising pulse engineering, we prepare molecular ground states in a few nanoseconds, ~100× faster than with gates. Back-of-the-envelope: Simulations can now tolerate T₁ and T₂ ~100× smaller.