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Fully frustrated Josephson junction ladders with Mobius boundary conditions as topologically protected qubits
No full textWe show how to realize a “protected” qubit by using a fullyfrustratedJosephsonjunctionladder (JJL) with Mobiusboundaryconditions. Such a system has been recently studied within a twisted conformal field theory (CFT) approach [G. Cristofano, G. Maiella, V. Marotta, Mod. Phys. Lett. A 15 (2000) 1679; G. Cristofano, G. Maiella, V. Marotta, G. Niccoli, Nucl. Phys. B 641 (2002) 547] and shown to develop the phenomenon of flux fractionalization [G. Cristofano, V. Marotta, A. Naddeo, G. Niccoli, Eur. Phys. J. B 49 (2006) 83]. The relevance of a “closed” geometry has been fully exploited in relating the topological properties of the ground state of the system to the presence of half flux quanta and the emergence of a topological order has been predicted [G. Cristofano, V. Marotta, A. Naddeo, J. Stat. Mech.: Theory Exp. (2005) P03006]. In this Letter the stability and transformation properties of the ground states under adiabatic magnetic flux change are analyzed and the deep consequences on the realization of a solid state qubit, protected from decoherence, are presented
A twisted conformal field theory description of dissipative quantum mechanics
No full textWe show how the recently proposed CFT for a bilayer quantum Hall system at filling View the MathML source [Mod. Phys. Lett. A 15 (2000) 1679; Nucl. Phys. B 641 (2002) 547; Phys. Lett. B 571 (2003) 250], the twisted model (TM), is equivalent to the system of two massless scalar bosons with a magnetic boundary interaction as introduced in [Nucl. Phys. B 443 (1995) 444], at the so-called “magic” points. We are then able to describe, within such a framework, the dissipativequantummechanics of a particle confined to a plane and subject to an external magnetic field normal to it. Such an analogy is further developed in terms of the TM boundary states, by describing the interaction between an impurity with a Hall system
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