Controlled-NOT logic with nonresonant Josephson phase qubits
نویسنده
چکیده
We establish theoretical bounds on qubit detuning for some of the previously proposed controlled-NOT !CNOT" logic gate implementations with weakly coupled Josephson phase qubits. It is found that in the twostep, #iSWAP-based case the value of the detuning during the entangling operations must not exceed 2g, where g is the characteristic coupling constant. In the single-step case we consider two practical, physically distinct implementations, in which one of the qubits is driven by a concurrent rf pulse of fixed frequency. We find that when the local drive is applied to the “reference” qubit !with which it is in resonance", the detuning should not exceed g. If the drive is applied to the “detuned” qubit, generation of the perfect CNOT gate is possible at any value of detuning provided that the amplitude of the pulse can be made arbitrarily large.
منابع مشابه
Controlled-NOT gate design for Josephson phase qubits with tunable inductive coupling: Weyl chamber steering and area theorem
Superconducting qubits with tunable coupling are ideally suited for fast and accurate implementation of quantum logic. Here we present a simple approach, based on Weyl chamber steering, to CNOT gate design for inductively coupled phase qubits with tunable coupling strength g. In the presence of simultaneous rf pulses on the individual qubits that appropriately track the coupling strength as it ...
متن کاملCoupling Josephson qubits via a current-biased information bus
– Josephson qubits without direct interaction can be effectively coupled by sequentially connecting them to an information bus: a current-biased large Josephson junction treated as an oscillator with adjustable frequency. The coupling between any qubit and the bus can be controlled by modulating the magnetic flux applied to that qubit. This tunable and selective coupling provides two-qubit enta...
متن کاملQuantum Process Tomography of a Universal Entangling Gate Implemented with Josephson Phase Qubits
Quantum logic gates must perform properly when operating on their standard input basis states, as well as when operating on complex superpositions of these states. Experiments using superconducting qubits have validated the truth table for particular implementations of e.g. the controlled-NOT gate 1,2 , but have not fully characterized gate operation for arbitrary superpositions of input states...
متن کاملQuantum two-level systems in Josephson junctions as naturally formed qubits.
The two-level systems (TLSs) naturally occurring in Josephson junctions constitute a major obstacle for the operation of superconducting phase qubits. Since these TLSs can possess remarkably long decoherence times, we show that such TLSs can themselves be used as qubits, allowing for a well controlled initialization, universal sets of quantum gates, and readout. Thus, a single current-biased Jo...
متن کاملControllable coherent population transfers in superconducting qubits for quantum computing
We propose an approach to coherently transfer populations between selected quantum states in one- and two-qubit systems by using controllable Stark-chirped rapid adiabatic passages. These evolution-time insensitive transfers, assisted by easily implementable single-qubit phase-shift operations, could serve as elementary logic gates for quantum computing. Specifically, this proposal could be con...
متن کامل