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arXiv:2005.12313 · Physical Review Research

Lack of a genuine time crystal in a chiral soliton model

Andrzej Syrwid, Arkadiusz Kosior, Krzysztof Sacha

Published Aug 17, 2020• 19 citations
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Abstract

In a recent publication [Phys. Rev. Lett. 124, 178902 (2020)], Öhberg and Wright claim that in a chiral soliton model it is possible to realize a genuine time crystal which corresponds to a periodic evolution of an inhomogeneous probability density in the lowest-energy state.We show that this result is incorrect and present a solution which possesses lower energy with the corresponding probability density that does not reveal any motion.It implies that the authors' conclusion that a genuine time crystal can exist in the system they consider is not true.

DOI
10.1103/physrevresearch.2.032038

Related papers

Response to comment on "Lack of a genuine time crystal in a chiral soliton model" by Öhberg and Wright

Andrzej Syrwid, Arkadiusz Kosior, Krzysztof Sacha

In the paper [Phys. Rev. Research 2, 032038] we have analyzed a chiral soliton model and shown that despite the claim of Öhberg and Wright [Phys. Rev. Lett. 124, 178902], there is no indication that a genuine quantum time crystal can be observed in the system. Here, we response to the recent comment on our paper written by Öhberg and Wright.

arXiv:2010.00414•Oct 1, 2020•1 citation

Comment on "Lack of a genuine time crystal in a chiral soliton model" by Syrwid, Kosior, and Sacha

Patrik Öhberg, Ewan M. Wright

We present a comment on A. Syrwid, A. Kosior, and K. Sacha, "Lack of a genuine time crystal in a chiral soliton model," arXiv:2005.12313.

arXiv:2008.10940•Aug 25, 2020•2 citations

Comment on “Quantum Time Crystals and Interacting Gauge Theories in Atomic Bose-Einstein Condensates”

Andrzej Syrwid, Arkadiusz Kosior, Krzysztof Sacha

In a recent Letter [Phys. Rev. Lett. 123, 250402PRLTAO0031-900710.1103/PhysRevLett.123.250402], Öhberg and Wright describe a Bose-Einstein condensate trapped on a ring in the presence of the density-dependent gauge potential. It is claimed that the ground state of the system corresponds to a rotating chiral bright soliton and consequently it forms a genuine time crystal which minimizes its energy by performing periodic motion. We show that the energy of the chiral soliton in the laboratory frame is not correctly calculated in the Letter. The correct energy becomes minimal if the soliton does not move.

arXiv:2002.11186•Physical Review Letters•Apr 29, 2020•22 citations

Response to comment on "Quantum time crystals and interacting gauge theories in atomic Bose-Einstein condensates" by Syrwid, Kosior, and Sacha

Patrik Öhberg, Ewan M. Wright

In a recent comment [1] on our paper [2] Syrwid, Kosior, and Sacha (SKS) asserted that we did not correctly calculate the chiral soliton energy ${\cal E}_{LAB}$ in the lab frame, and further that the system we proposed is not capable of supporting a genuine quantum time crystal. We concede that we did not correctly calculate ${\cal E}_{LAB}$ but we illustrate below that our system can nonetheless display time crystal behavior with a ground state that is spatially localized and rotating.

arXiv:2003.05655•Mar 12, 2020•1 citation

Comment on "Quantum Time Crystals from Hamiltonians with Long-Range Interactions"

Vedika Khemani, Roderich Moessner, Shivaji L. Sondhi

In a recent paper (Phys. Rev. Lett. 123, 210602), Kozin and Kyriienko claim to realize "genuine" ground state time crystals by studying models with long-ranged and infinite-body interactions. Here we point out that their models are doubly problematic: they are unrealizable ${\it and}$ they violate well established principles for defining phases of matter. Indeed with infinite body operators allowed, almost all quantum systems are time crystals. In addition, one of their models is highly unstable and another amounts to isolating, via fine tuning, a single degree of freedom in a many body system--allowing for this elevates the pendulum of Galileo and Huygens to a genuine time crystal.

arXiv:2001.11037•Jan 29, 2020•5 citations

Simulation of time crystal behavior for a few boson chiral soliton model in a ring

Patrik Öhberg, Ewan M. Wright

We present numerical simulations for a chiral soliton model with N=2,3 bosons in a ring, this being a few-particle version of our previous mean-field model for a quantum time crystal. Following Syrwid, Kosior, and Sacha (SKS), the notion is that a precise position measurement of one particle can lead to spontaneous formation of a bright soliton that in a time crystal should rotate intact for at least a few revolutions around the ring. In their work SKS find spontaneous formation of a soliton due to the position measurement, but quantum fluctuations cause the soliton to subsequently decay before it has a chance to perform even one revolution of the ring. Based on this they conclude that time crystal dynamics are impossible. In contrast, for our few boson chiral soliton model, and allowing for imprecise (weak) measurements of the particle position, we show that time crystal behavior is possible allowing for several revolutions of the spontaneously formed soliton around the ring. We therefore argue that our chiral soliton model can realize a quantum time crystal when weak position measurements are allowed for.

arXiv:2401.04843•Jan 9, 2024•0 citations
In a recent publication [Phys. Rev. Lett. 124, 178902 (2020)], Öhberg and Wright claim that in a chiral soliton model it is possible to realize a genuine time crystal which corresponds to a periodic evolution of an inhomogeneous probability density in the lowest-energy state.We show that this result is incorrect and present a solution which possesses lower energy with the corresponding probability density that does not reveal any motion.It implies that the authors' conclusion that a genuine time crystal can exist in the system they consider is not true.
In a recent Letter [Phys. Rev. Lett. 123, 250402PRLTAO0031-900710.1103/PhysRevLett.123.250402], Öhberg and Wright describe a Bose-Einstein condensate trapped on a ring in the presence of the density-dependent gauge potential. It is claimed that the ground state of the system corresponds to a rotating chiral bright soliton and consequently it forms a genuine time crystal which minimizes its energy by performing periodic motion. We show that the energy of the chiral soliton in the laboratory frame is not correctly calculated in the Letter. The correct energy becomes minimal if the soliton does not move.
In a recent comment [1] on our paper [2] Syrwid, Kosior, and Sacha (SKS) asserted that we did not correctly calculate the chiral soliton energy ELAB{\cal E}_{LAB}ELAB​ in the lab frame, and further that the system we proposed is not capable of supporting a genuine quantum time crystal. We concede that we did not correctly calculate ELAB{\cal E}_{LAB}ELAB​ but we illustrate below that our system can nonetheless display time crystal behavior with a ground state that is spatially localized and rotating.
In a recent paper (Phys. Rev. Lett. 123, 210602), Kozin and Kyriienko claim to realize "genuine" ground state time crystals by studying models with long-ranged and infinite-body interactions. Here we point out that their models are doubly problematic: they are unrealizable and{\it and}and they violate well established principles for defining phases of matter. Indeed with infinite body operators allowed, almost all quantum systems are time crystals. In addition, one of their models is highly unstable and another amounts to isolating, via fine tuning, a single degree of freedom in a many body system--allowing for this elevates the pendulum of Galileo and Huygens to a genuine time crystal.
We present numerical simulations for a chiral soliton model with N=2,3 bosons in a ring, this being a few-particle version of our previous mean-field model for a quantum time crystal. Following Syrwid, Kosior, and Sacha (SKS), the notion is that a precise position measurement of one particle can lead to spontaneous formation of a bright soliton that in a time crystal should rotate intact for at least a few revolutions around the ring. In their work SKS find spontaneous formation of a soliton due to the position measurement, but quantum fluctuations cause the soliton to subsequently decay before it has a chance to perform even one revolution of the ring. Based on this they conclude that time crystal dynamics are impossible. In contrast, for our few boson chiral soliton model, and allowing for imprecise (weak) measurements of the particle position, we show that time crystal behavior is possible allowing for several revolutions of the spontaneously formed soliton around the ring. We therefore argue that our chiral soliton model can realize a quantum time crystal when weak position measurements are allowed for.