A common thread of my research effort is the study and engineering of cooperative mechanisms. I studied superradiance and other emergent phenomena arising in solid-state cavity quantum electrodynamics (QED). I also develop scientific software, focusing on ways in which the research community can cooperatively contribute, empowering science at scale.
More precisely, I actively pursue different lines of research: open-source quantum software, quantum error mitigation, and cooperative effects in driven-dissipative open quantum systems out of equilibrium.
You can find the full list of publications here.
Open-source quantum software
I develop and maintain open-source software that implements numerical methods with applications in “quantum technology” and quantum optics and quantum compting research.
I am one of the creators and maintainers of Mitiq, a quantum error mitigation toolkit in Python. Since 2018, I am a contributor to (and now admin of) QuTiP, the quantum toolbox in Python, for which I co-developed the PIQS module, which uses permutational symmetry to reduce the computational resources required to describe effectively collective dynamics.
I see open-source software development more as a method than a proper theme of research, but on the other side, the numerical perspective it provides does affect the way one can see a problem. For example, the Liouvillian superoperator describing an open quantum system dynamics can be seen not only as a linear functional but also represented with a concrete matrix, whose properties can be numerically studied, such as its spectrum and eigenstates.
R. LaRose et al., arXiv:2009.04417, Mitiq
H. Silvério & S. Grijalva et al., Quantum 6, 629 (2022) Link, Pulser
B. Li et al., Quantum 6, 630 (2022) Link, QuTiP-QIP
N. Shammah et al., Physical Review A 98, 063815 (2018), PIQS
More info in the Code page.
Quantum Error Mitigation
I am interested in how we can improve the performance of noisy quantum computers with theoretical methods and software tools. Quantum error mitigation is an alternative approach to quantum error correction that does not bring similar overheads in terms of qubits – at the cost of higher sampling overhead. I am interested in designing various approaches at the gate (digital) level and benchmarking against quantum processing units of different architectures (as different hardware experiences different noise). Quantum error mitigation can also be used to hybridize quantum error correction schemes and adopt them with higher level of noise.
M. Wahl et al., arXiv:2304.14985.
R. LaRose et al., Quantum 6, 774 (2022).
K. Schultz et al., Phys. Rev. A 106, 052406 (2022).
B. McDonough et al., ACM/IEEE Int Workshop QCS (2022).
A. Mari et al., Phys. Rev. A 104, 052607 (2021).
Out-of-equilibrium many body quantum systems: Superradiance and cooperative phenomena
I am interested in the emerging dynamics of many-body quantum systems out of equilibrium. While at-equilibrium physics is well described by standard thermodynamics, out-of equilibrium systems, under external drive and undergoing dissipation, represent a much less characterized system model. I am interested in particular in macroscopic quantum effects, such as light emission induced by quantum vacuum instabilities in cavity QED, spin squeezing, superradiance, and chaos.
To tackle these problems I exploit symmetries of the models that can allow a feasible numerical approach by representing the dynamics with more compact algebraic operators and superoperators.
G.-Q. Zhang et al., PRX Quantum 2, 020307 (2021).
G. Piccitto et al., Physical Review B 104, 014307 (2021)
D. Huybrechts et al., Physical Review B 101, 214302 (2020)
N. Shammah et al., Physical Review A 98, 063815 (2018)
N. Shammah et al. Physical Review A 96, 023863 (2017)
Solid-state photonics and polaritonics
There has been considerable advancement in optoelectronic solid-state devices where light and matter hybridize to form quasiparticles known as polaritons. The same heterostructure technology has been used to engineer artificial quantum atoms with broken inversion symmetry, which opens up the possibility for unconventional light emission. Applications include Terahertz light emission, a range where there is a “technology gap” in our capability of detecting and emitting electromagnetic waves.
I use analytical techniques in perturbation theory and with non-perturbative approaches to treat the many-body physics of these electronic and photonic systems, which can often be described as a two-dimensional electron gas (2DEG) interacting with a photonic field.
M. Cirio et al., Physical Review Letters 122, 190403 (2019)
N. Shammah and S. De Liberato, Physical Review B 92, 201402 Rapid Comm. (2015)
N. Shammah et al., Physical Review B 89, 235309 (2014)
Nathan Shammah 