REVIEW 9 cited by
Strong-to-Weak Spontaneous Symmetry Breaking in Mixed Quantum States
Not yet reviewed by Pith; the record is open.
This paper has not been read by Pith yet. Machine review is queued; the pith claim, tier, and objections will appear here once it completes.
SPECIMEN: schema-true, not a live event
T0 review · schema-true
One-sentence machine reading of the paper's core claim.
pith:XXXXXXXX · record.json · timestamp
read the original abstract
Symmetry in mixed quantum states can manifest in two distinct forms: strong symmetry, where each individual pure state in the quantum ensemble is symmetric with the same charge, and weak symmetry, which applies only to the entire ensemble. This paper explores a novel type of spontaneous symmetry breaking (SSB) where a strong symmetry is broken to a weak one. While the SSB of a weak symmetry is measured by the long-ranged two-point correlation function, the strong-to-weak SSB (SW-SSB) is measured by the fidelity correlator. We prove that SW-SSB is a universal property of mixed-state quantum phases, in the sense that the phenomenon of SW-SSB is robust against symmetric low-depth local quantum channels. We also show that the symmetry breaking is "spontaneous" in the sense that the effect of a local symmetry-breaking measurement cannot be recovered locally. We argue that a thermal state at a nonzero temperature in the canonical ensemble (with fixed symmetry charge) should have spontaneously broken strong symmetry. Additionally, we study non-thermal scenarios where decoherence induces SW-SSB, leading to phase transitions described by classical statistical models with bond randomness. In particular, the SW-SSB transition of a decohered Ising model can be viewed as the "ungauged" version of the celebrated toric code decodability transition. We confirm that, in the decohered Ising model, the SW-SSB transition defined by the fidelity correlator is the only physical transition in terms of channel recoverability. We also comment on other (inequivalent) definitions of SW-SSB, through correlation functions with higher Renyi indices.
Forward citations
Cited by 9 Pith papers
-
Non-perturbative constraints on stability and renormalization group flows in nonequilibrium matter
CMI scaling function is monotonically non-increasing along RG flows in nonequilibrium systems, forbidding flows from lower to higher CMI fixed points.
-
Mixed-state phases from local reversibility
Locally reversible channel circuits define a refined mixed-state phase equivalence under which the 2D classical loop ensemble is non-trivially ordered, with topological degeneracy protected.
-
Confinement as Decoding: Higher Form Codes and Lattice Yang-Mills Theory
Decoding a higher-form quantum code with Wilson-line noise is the same computation as comparing center-twisted Yang-Mills partition functions; the paper works out this dictionary and its strong-coupling consequences.
-
Exploring Entropic Orders: High Temperature Continuous Symmetry Breaking, Chiral Topological States and Local Commuting Projector Models
New analytic constructions yield quantum lattice models with continuous symmetry breaking and chiral topological order at arbitrarily high temperatures via entropic stabilization.
-
Effective field theory for dissipative photons from higher-form symmetries
A Schwinger-Keldysh effective action built on spontaneously broken higher-form symmetry gives dissipative Maxwell equations with an entropy current for photons in insulators.
-
Spacetime duality between sequential and measurement-feedback circuits
Sequential unitary and measurement-feedback circuits for preparing GHZ, topological, and fractal states are spacetime-dual, linking Kramers-Wannier duality to Z2 gauging and enabling constant-qubit order measurements.
-
Topological Holography for Mixed-State Phases and Phase Transitions
Mixed-state phases of (1+1)D systems with finite group symmetry are classified by condensable algebras in the doubled topological order Z(Vec_{GxG}) subject to Hermiticity and positivity constraints.
-
Detection of 2D SPT phases under decoherence
A partial-symmetry order parameter, J_{g,h,M}, is shown to extract the SPT invariants of two-dimensional mixed states protected jointly by strong and weak symmetries in CZX-type models.
-
Diagnosing 2D symmetry protected topological states via mixed state anomaly
The RDM of a 2D Z2 SPT state acts as a 1D anomalous mixed state whose twisted disorder parameter contains a quantized topological constant (D=4 with time reversal) and supports symmetry-breaking-type long-range order.
Discussion (0). Sign in to comment.