Generalised uncertainty relations from finite-accuracy measurements

In this short note we show how the Generalised Uncertainty Principle (GUP) and the Extended Uncertainty Principle (EUP), two of the most common generalised uncertainty relations proposed in the quantum gravity literature, can be derived within the context of canonical quantum theory, without the need for modified commutation relations. A generalised uncertainty principle-type relation naturally emerges when the standard position operator is replaced by an appropriate Positive Operator Valued Measure (POVM), representing a finite-accuracy measurement that localises the quantum wave packet to within a spatial region sigma(g) > 0. This length scale is the standard deviation of the envelope function, g, that defines the positive operator valued measure elements. Similarly, an extended uncertainty principle-type relation emerges when the standard momentum operator is replaced by a positive operator valued measure that localises the wave packet to within a region (sigma) over tilde (g) > 0 in momentum space. The usual generalised uncertainty principle and extended uncertainty principle are recovered by setting sigma(g) similar or equal to root hG/c(3), the Planck length, and (sigma) over tilde (g) similar or equal to root h root Lambda/3, where Lambda is the cosmological constant. Crucially, the canonical Hamiltonian and commutation relations, and, hence, the canonical Schrodinger and Heisenberg equations, remain unchanged. This demonstrates that generalised uncertainty principle and extended uncertainty principle phenomenology can be obtained without modified commutators, which are known to lead to various pathologies, including violation of the equivalence principle, violation of Lorentz invariance in the relativistic limit, the reference frame-dependence of the "minimum" length, and the so-called soccer ball problem for multi-particle states.