ELFT HÍRADÓ

[Dr.Pályi András <palyi.andras AT ttk.bme.hu>]

Dear Colleagues,

This is to announce the following seminar talk taking place tomorrow 
afternoon at BME.

Schroedinger cat in a silicon box: quantum information and quantum foundations
Prof. Andrea Morello
School of Electrical Engineering and Telecommunications, UNSW Sydney, 
Australia

Time: Sep 26th Friday, 14:15
Location: BME F building, stairway III, seminar room of the Department of 
Theoretical Physics

Abstract:
I will present recent experiments, and exciting new directions, for the use 
of high-spin nuclei in silicon for quantum information, quantum foundations, 
and spin-mechanics entanglement. Nuclear spins in silicon are among the most 
coherent quantum objects to be found in the solid state. They have infinite 
relaxation time, and second-scale coherence time [1]. By using the I=7/2, 
8-dimensional nucleus of antimony [2], we have prepared a nuclear 
Schroedinger cat within a functional nanoelectronic device [3]. This can be 
used to encode a cat-qubit similar to the bosonic encodings used in microwave 
cavities, but with atomic size, and even more extreme noise bias.
Recent work on the simpler phosphorus atoms has shown the ability to entangle 
nuclear spins that are not bound to the same electron [4]. As the next step 
for scaling up donor quantum processors, we are working to integrate the 
donors with lithographic quantum dots, and I will present preliminary results 
in that direction.
We then used the Schroedinger cat and other nonclassical states to perform a 
curious experiment, where the quantumness of the state is certified by 
monitoring its uniform precession, in seeming contradiction with Ehrenfest's 
theorem [4].
High-spin nuclei possess a quadrupole moment that couples them to lattice 
strain [5]. I will discuss plans to entangle a single nuclear spin with a 
MHz-range mechanical oscillator, and perspectives to scale up the mass of the 
oscillator to test gravitational collapse models.
[1] J. Muhonen et al., Nature Nanotechnology 9, 986 (2014)
[2] S. Asaad, V. Mourik et al., Nature 579, 205 (2020)
[3] X. Yu et al., Nature Physics 21, 362 (2025)
[4] H. Stemp et al, Science 389, 1234 (2025)
[5] A. Vaartjes et al., Newton 1, 100017 (2025)
[6] L. O'Neill et al., Applied Physics Letters 119, 174001 (2021)

More information on Prof. Morello:
https://en.wikipedia.org/wiki/Andrea_Morello
https://scholar.google.com/citations?user=_G8qcyEAAAAJ&hl=hu&oi=ao

Best regards,
Andras Palyi