Research

My research is motivated and inspired by the rapid development of experimental setups in which many-body quantum systems can be controlled to a high level of precision, allowing one to use them for quantum simulation, computation, or metrology. For a complete list of publications please refer to arXiv or google scholar.

(Many-body) quantum information theory #

Understanding the complexity of quantum many-body problems is a fascinating endeavour. With the advent of quantum computational devices, it also becomes increasingly relevant practically. A major frontier is to delineate the boundaries between problems that can efficiently be solved classically, those that can only be solved quantumly, and those that cannot be solved (efficiently) at all.

I am particularly interested in computational problems from quantum many-body physics, such as quantum dynamics or ground states. What I particularly enjoy about this line of research is that progress on this question comes in many forms, for example in terms of an efficient (quantum or classical) algorithm for one sort of problem, from constructing hard instances of problems, or from looking at their average difficulty (e.g., in random circuits).

Read more about many-body physics and information.

Selected/recent publications

1. Constraints on phantom codes from automorphism group bounds
   Morris, Malz, arXiv (04/2026)
2. Measurement-induced entanglement in noisy 2D random Clifford circuits
   Wei, Nelson, Rajakumar, Cruz, Gorshkov, Gullans, Malz, arXiv (10/2025)
3. Computational complexity of injective projected entangled pair states
   Harley, Witteveen, Malz, arXiv (09/2025)
4. Quantum and Classical Dynamics with Random Permutation Circuits
   Bertini, Klobas, Kos, Malz, PRX (2025), arXiv
5. Measurement-induced entanglement and complexity in random constant-depth 2D quantum circuits
   McGinley, Ho, Malz, PRX (2025), arXiv
6. Computational complexity of isometric tensor network states
   Malz, Trivedi, PRX Quantum (2025), arXiv (2024)

Quantum optics #

In quantum optics, we study the interaction between atoms (or few-level systems in general) with light (a bosonic field). This is a reasonably mature field, and its achievements have paved the way to the astonishing quantum devices we have today. Current frontiers in quantum optics include building better quantum devices (computers, sensors, light sources) and understanding the non-equilibrium many-body physics in open quantum systems.

I have worked in quantum optics since the start of my PhD with Andreas Nunnenkamp, and therefore covered a diverse set of topics. Read more about quantum optics.

Selected/recent publications

1. Unraveling Superradiance: Entanglement and Mutual Information in Collective Decay
   Zhang, Malz, Rabl, PRL (2025), arXiv
2. Effects of retardation on many-body superradiance in chiral waveguide QED
   Windt, Bello, Malz, Cirac, PRL (2025), arXiv
3. Efficient tensor network simulation of multi-emitter non-Markovian systems
   Papaefstathiou, Malz, Cirac, Bañuls, PRA (2025), arXiv
4. Large-N limit of Dicke superradiance
   Malz, Trivedi, Cirac, PRA (2022), arXiv
5. Anomalous Behaviors of Quantum Emitters in Non-Hermitian Baths
   Gong, Bello, Malz, Kunst, PRL (2022), arXiv
6. Quantum-Limited Directional Amplifiers with Optomechanics
   Malz, et al., PRL (2018)

State preparation algorithms #

Whether it is computing the time evolution of a system or finding its ground state, state preparation is a key step in many quantum algorithms. We work on this problem predominantly in the context of tensor network states, which constitute a versatile family of states that are known to approximate ground states of local Hamiltonians well.

In one dimension, these states are known as MPS, and we have recently proven that essentially all of them (with some asterisks) can prepared very efficiently and also provided an algorithm to do so [1]. In two and higher dimensions, we have introduced an adiabatic path to produce many states including the AKLT state [2], and studied states that can be prepared using sequential circuits, which, as we showed, include many important states such as ground states of many topological models [3]. We have also applied this understanding to preparing entangled photonic states [4]. You can read more here.

Selected publications

1. Preparation of matrix product states with log-depth quantum circuits
   Malz*, Styliaris*, Wei*, Cirac, PRL (2024), arXiv
2. Efficient Adiabatic Preparation of Tensor Network States
   Wei*, Malz*, Cirac, PRR (2023), arXiv
3. Sequential generation of projected entangled-pair states
   Wei, Malz, Cirac, PRL (2022), arXiv
4. Deterministic generation of two-dimensional multi-photon cluster states
   O’Sullivan, …, Wallraff, ncomms (2025), arXiv

Analogue quantum simulation #

Analogue simulators are specialized devices that natively implement a certain Hamiltonian of interest. This makes them more limited than fault-tolerant quantum computers (a classical analogue would be a wind tunnel versus your laptop), but their big advantage is that they exist. The most successful such simulators are based on atoms in optical lattices.

I like to ask how we can go beyond existing experimental capabilities, for example, by using subwavelength atomic arrays or Rydberg dressing to achieve long-range interactions [3, 4, 5], or by using insights from learning theory to extract more information from existing experiments [1,2].

Read more about analogue quantum simulation.

Selected publications

1. Estimating applied potentials in cold-atom lattice simulators
   Kumar, Malz, PRA (2026), arXiv
2. Gaussian tomography for cold-atom simulators
   Kiser, McGinley, Malz, arXiv:2510.23591
3. Few-Body Analog Quantum Simulation with Rydberg-Dressed Atoms in Optical Lattices
   Malz, Cirac, PRX Q (2023), arXiv
4. Atomic waveguide QED with atomic dimers
   Castells-Graells, Malz, Rusconi, Cirac, PRA (2021), arXiv
5. Topological Two-Dimensional Floquet Lattice on a Single Superconducting Qubit
   Malz, Smith, PRL (2021), arXiv.