Scrambling Transition in a Radiative Random Unitary Circuit

Area of Science:

• Quantum Information Science
• Condensed Matter Physics
• Quantum Computing

Background:

• Quantum information scrambling describes how quantum information spreads within a quantum system.
• Understanding information dynamics in open quantum systems is crucial for quantum technologies.
• Random unitary circuits provide a model for studying complex quantum dynamics.

Purpose of the Study:

• To investigate quantum information scrambling in a random unitary circuit with environmental interaction.
• To identify and characterize a nonequilibrium phase transition in quantum information dynamics.
• To explore the information-theoretic consequences of scrambling and the phase transition on information retrieval.

Main Methods:

• Utilizing the out-of-time-order correlator (OTOC) to quantify quantum scrambling.
• Analyzing a random unitary circuit model with tunable qubit-environment exchange rate (p).
• Developing and applying a decoding scheme to assess information recovery from radiated qubits.

Main Results:

• A nonequilibrium phase transition in the directed percolation universality class at a critical swap rate (p_c).
• Ballistic growth of the OTOC for p < p_c, indicating system-internal scrambling.
• Uniform vanishing of the OTOC for p > p_c, signifying information transfer to the environment.
• Coincident transition in operator spreading and the ability to decode initial quantum information from radiated qubits.
• Observation of an entanglement transition in coherent information based on the initial state of swapped-in qubits.

Conclusions:

• The study reveals a critical transition in quantum information scrambling behavior.
• This transition directly affects the recoverability of initial quantum information from the environment.
• The findings have implications for understanding information flow in open quantum systems and quantum information processing.