Linear growth of quantum circuit complexity

J Haferkamp, P Faist, NBT Kothakonda, J Eisert… - Nature Physics, 2022 - nature.com
The complexity of quantum states has become a key quantity of interest across various
subfields of physics, from quantum computing to the theory of black holes. The evolution of …

Random unitaries in extremely low depth

T Schuster, J Haferkamp, HY Huang - arxiv preprint arxiv:2407.07754, 2024 - arxiv.org
We prove that random quantum circuits on any geometry, including a 1D line, can form
approximate unitary designs over $ n $ qubits in $\log n $ depth. In a similar manner, we …

Random quantum circuits are approximate unitary -designs in depth

J Haferkamp - Quantum, 2022 - quantum-journal.org
The applications of random quantum circuits range from quantum computing and quantum
many-body systems to the physics of black holes. Many of these applications are related to …

Models of quantum complexity growth

FGSL Brandão, W Chemissany, N Hunter-Jones… - PRX Quantum, 2021 - APS
The concept of quantum complexity has far-reaching implications spanning theoretical
computer science, quantum many-body physics, and high-energy physics. The quantum …

Designs from Local Random Quantum Circuits with Symmetry

Z Li, H Zheng, J Liu, L Jiang, ZW Liu - PRX Quantum, 2024 - APS
The generation of k-designs (pseudorandom distributions that emulate the Haar measure up
to k moments) with local quantum circuit ensembles is a problem of fundamental importance …

Entanglement entropy production in quantum neural networks

M Ballarin, S Mangini, S Montangero… - Quantum, 2023 - quantum-journal.org
Abstract Quantum Neural Networks (QNN) are considered a candidate for achieving
quantum advantage in the Noisy Intermediate Scale Quantum computer (NISQ) era. Several …

On the average-case complexity of learning output distributions of quantum circuits

A Nietner, M Ioannou, R Sweke, R Kueng… - arxiv preprint arxiv …, 2023 - arxiv.org
In this work, we show that learning the output distributions of brickwork random quantum
circuits is average-case hard in the statistical query model. This learning model is widely …

Projected least-squares quantum process tomography

T Surawy-Stepney, J Kahn, R Kueng, M Guta - Quantum, 2022 - quantum-journal.org
We propose and investigate a new method of quantum process tomography (QPT) which we
call projected least squares (PLS). In short, PLS consists of first computing the least-squares …

Fastest local entanglement scrambler, multistage thermalization, and a non-Hermitian phantom

J Bensa, M Žnidarič - Physical Review X, 2021 - APS
We study random quantum circuits and their rate of producing bipartite entanglement,
specifically with respect to the choice of 2-qubit gates and the order (protocol) in which these …

Approximate Unitary -Designs from Shallow, Low-Communication Circuits

N LaRacuente, F Leditzky - arxiv preprint arxiv:2407.07876, 2024 - arxiv.org
Random unitaries are useful in quantum information and related fields but hard to generate
with limited resources. An approximate unitary $ k $-design is an ensemble of unitaries and …