TY - JOUR
T1 - Measuring the adiabatic non-Hermitian Berry phase in feedback-coupled oscillators
AU - Singhal, Yaashnaa
AU - Martello, Enrico
AU - Agrawal, Shraddha
AU - Ozawa, Tomoki
AU - Price, Hannah
AU - Gadway, Bryce
N1 - Acknowledgments. We thank Barry Bradlyn for helpful discussions. This material (Y.S., S.A., B.G.) is based upon work supported by the National Science Foundation under Grant No. 1945031. Y.S. acknowledges support by the Philip J. and Betty M. Anthony Undergraduate Research Award and the Jeremiah D. Sullivan Undergraduate Research Award of the UIUC Department of Physics. T.O. acknowledges support from JSPS KAKENHI Grant No. JP20H01845, JST PRESTO Grant No. JPMJPR19L2, JST CREST Grant No. JPMJCR19T1, and RIKEN iTHEMS. E.M. and H.M.P. are supported by the Royal Society via Grants No. UF160112, No. RGF\EA\180121, and No. RGF\R1\180071. E.M. and H.M.P. are also supported by the Engineering and Physical Sciences Research Council (Grant No. EP/W016141/1). This work was also supported by the BRIDGE Seed Fund for collaboration between the University of Birmingham and the University of Illinois at Urbana-Champaign.
PY - 2023/7
Y1 - 2023/7
N2 - The geometrical Berry phase is key to understanding the behavior of quantum states under cyclic adiabatic evolution. When generalized to non-Hermitian systems with gain and loss, the Berry phase can become complex and should modify not only the phase but also the amplitude of the state. Here, we perform the first experimental measurements of the adiabatic non-Hermitian Berry phase, exploring a minimal two-site PT-symmetric Hamiltonian that is inspired by the Hatano-Nelson model. We realize this non-Hermitian model experimentally by mapping its dynamics to that of a pair of classical oscillators coupled by real-time measurement-based feedback. As we verify experimentally, the adiabatic non-Hermitian Berry phase is a purely geometrical effect that leads to significant amplification and damping of the amplitude also for noncyclical paths within the parameter space even when all eigenenergies are real. We further observe a non-Hermitian analog of the Aharonov-Bohm solenoid effect, observing amplification and attenuation when encircling a region of broken PT symmetry that serves as a source of imaginary flux. This experiment demonstrates the importance of geometrical effects that are unique to non-Hermitian systems and paves the way towards further studies of non-Hermitian and topological physics in synthetic metamaterials.
AB - The geometrical Berry phase is key to understanding the behavior of quantum states under cyclic adiabatic evolution. When generalized to non-Hermitian systems with gain and loss, the Berry phase can become complex and should modify not only the phase but also the amplitude of the state. Here, we perform the first experimental measurements of the adiabatic non-Hermitian Berry phase, exploring a minimal two-site PT-symmetric Hamiltonian that is inspired by the Hatano-Nelson model. We realize this non-Hermitian model experimentally by mapping its dynamics to that of a pair of classical oscillators coupled by real-time measurement-based feedback. As we verify experimentally, the adiabatic non-Hermitian Berry phase is a purely geometrical effect that leads to significant amplification and damping of the amplitude also for noncyclical paths within the parameter space even when all eigenenergies are real. We further observe a non-Hermitian analog of the Aharonov-Bohm solenoid effect, observing amplification and attenuation when encircling a region of broken PT symmetry that serves as a source of imaginary flux. This experiment demonstrates the importance of geometrical effects that are unique to non-Hermitian systems and paves the way towards further studies of non-Hermitian and topological physics in synthetic metamaterials.
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U2 - 10.1103/PhysRevResearch.5.L032026
DO - 10.1103/PhysRevResearch.5.L032026
M3 - Article
AN - SCOPUS:85169292912
SN - 2643-1564
VL - 5
JO - Physical Review Research
JF - Physical Review Research
IS - 3
M1 - L032026
ER -