Vanishing of the negative-sign problem of quantum Monte Carlo simulations in one-dimensional frustrated spin systems

We have solved the negative-sign problem in a general frustrated double-spin-chain system, namely the (Formula presented)-(Formula presented)-(Formula presented)-(Formula presented) model. This is made possible by changing the representation basis from the conventional (Formula presented) basis to a dimer basis that has the spin-reversal symmetry. The necessary condition for the problem to disappear in this new basis is (Formula presented). Frustration is the origin only in the conventional (Formula presented) basis. We demonstrate the efficiency of this new basis at the transition point between the gapless spin-fluid phase and the gapped dimer phase.