Abstrac The performance of today’s quantum computers are affected by noise. This effect can be analyzed in the result of simple quantum algorithms in real quantum computers. The noise can be characterized as a decoherence error or a systematic error, the last could be corrected by a unitary rotation. In this article we propose two methods to model a systematic error, in the Quantum Fourier Transform algorithm (QFT). The first method uses the isotropic index presented in [1] and needs to reconstruct the density matrix of the experimental state, while the second method, although less general, only needs to reconstruct the reduced density matrices for each qubit. In both methods, a unitary transformation is proposed, which approximates the experimental result to the expected theoretical state. As an example, the QFT algorithm is analyzed for two qubit states, in quantum IBM Q computer ibmq_santiago.

Using the methods for optimal simulation of quantum logic gates, we perform a quantitative estimation of the time resources involved in the execution of universal gate sets for the case of three representative models of quantum computation based on global control. The importance of such models stems from the solution to the problem of experimentally addressing and locally manipulating the qubits in a given quantum register. The numerical estimation of the temporal efficiency for each model is performed by assuming that the qubits in the register can be coupled to each other via the Ising and the Förster interactions. Finally, we discuss the feasibility of the physical realization of such architectures under quantum error correction conditions.

The goal of this paper is to review the theoretical basis for achieving a faithful quantum information transmission and processing in the presence of noise. Initially, encoding and decoding, implementing gates and quantum error correction will be considered error-free. Finally, we shall relax this non-realistic assumption, introducing the quantum fault-tolerant concept. The existence of an error threshold permits us to conclude that there is no physical law preventing a quantum computer from being built. An error model based on the depolarising channel will be able to provide a simple estimate of the storage or memory computation error threshold: ηth < 5.2 10-5. The encoding is made by means of the [[7,1,3]] Calderbank-Shor-Steane quantum code, and Shor's fault-tolerant method is used to measure the stabiliser's generators.

El objetivo de este artículo es la revisión de los fundamentos teóricos que permiten una correcta transmisión y procesado de la información cuántica en presencia de ruido. Inicialmente, los procesos de codificación, decodificación, aplicación de puertas y corrección de errores se consideraran sin error. Finalmente relajaremos esta consideración no realista, lo que conducirá al concepto de tolerancia a fallos. La existencia de un umbral de error permite concluir que no hay ninguna ley física que impida construir un ordenador cuántico. Mediante un modelo de error basado en un canal despolarizante, se hará una estimación simple para el umbral de los errores de memoria: ηth < 5.2 10-5. La codificación se realiza mediante un código cuántico [[7,1,3]] de Calderbank-Shor-Steane, y se usa el método de Shor tolerante a fallos para medir los generadores del estabilizador.