Quantum complexity theory

The purported power of quantum computers and our excitement over studying quantum systems come from our belief that large physically realistic quantum systems cannot be efficiently simulated on classical computers. Our group is interested in classifying which quantum states are hard to simulate on classical computers and which ones are easy. This applies to all kinds of quantum states of qubits, bosons, or fermions, including thermal states, steady states, states following time evolution under a Hamiltonian, a Lindbladian, or a circuit, subject to noise and/or mid-circuit measurements, etc... Of particular interest are transitions between easiness and hardness.