We provide necessary and sufficient conditions for states to have an arbitrarily small uncertainty product of the azimuthal angle φ and its canonical moment Lz. We illustrate our results with analytical examples.
The description of a quantum system in terms of angle variables may violate Heisenberg uncertainty principle. The familiar case is the azimutal angle ϕ and its canonical moment Lz. Although this problem was foreseen almost a century ago, up to the present days there are no criteria to precisely characterize the violation. In this paper, we present a theorem which provides necessary and sufficient conditions for the violation of the Heisenberg uncertainty principle. We illustrate our results with analytical examples.
The equality in the uncertainty principle for linear momentum and position is obtained for states which also minimize the uncertainty product. However, in the uncertainty relation for angular momentum and angular position both sides of the inequality are state dependent and therefore the intelligent states, which satisfy the equality, do not necessarily give a minimum for the uncertainty product. In this paper, we highlight the difference between intelligent states and minimum uncertainty states by investigating a class of intelligent states which obey the equality in the angular uncertainty relation while having an arbitrarily large uncertainty product. To develop an understanding for the uncertainties of angle and angular momentum for the large-uncertainty intelligent states we compare exact solutions with analytical approximations in two limiting cases.
The Heisenberg uncertainty relation, concerning the product of the standard deviations of position and momentum, is studied for a quantum oscillator characterized by deformed boson algebra. Special forms of the deformed number operator are determined such that the ground state and any deformed coherent state of the oscillator under study exhibit minimum uncertainty, as the canonical boson algebra provides, but the product of the corresponding standard deviations is less than the canonical lower bound, ℏ/2. Above all, each standard deviation and, consequently, the uncertainty become arbitrarily small for the ground state, other states of the Fock basis, and deformed coherent states with arbitrarily small magnitude of the label, if the parameters defining the special deformed number operator are properly chosen.