|Title:||Quantum Gross-Pitaevskii Equation|
|Author(s):||Jutho Haegeman, Damian Draxler, Vid Stojevic, J. Ignacio Cirac, Tobias J. Osborne, Frank Verstraete|
|As Contributors:||Jutho Haegeman|
|Submitted by:||Haegeman, Jutho|
|Submitted to:||SciPost Physics|
|Subject area:||Quantum Physics|
We introduce a non-commutative generalization of the Gross-Pitaevskii equation for one-dimensional quantum gasses and quantum liquids. This generalization is obtained by applying the time-dependent variational principle to the variational manifold of continuous matrix product states. This allows for a full quantum description of many body system ---including entanglement and correlations--- and thus extends significantly beyond the usual mean-field description of the Gross-Pitaevskii equation, which is known to fail for (quasi) one-dimensional systems. By linearizing around a stationary solution, we furthermore derive an associated generalization of the Bogoliubov -- de Gennes equations. This framework is applied to compute the steady state response amplitude to a periodic perturbation of the potential.
We have extended the discussion of the periodic potential example. We clearly indicate how our framework improves upon the mean field prediction (Bogoliubov theory), which is also shown in the plot. We also discuss the underlying physics that shows up in the response amplitude, namely the signature of the low-lying excitations in the system, which are known to be Lieb's Type I and Type II excitations. Whereas Bogoliubov theory can only access the first type, our method also captures the effect of the second type, which is important at stronger interactions.