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Quantum Electronics and Laser Science Conference

Entangled states of trapped atoms for quantum logic and spectroscopy

Christopher R. Monroe, D. M. Meekhof, B. E. King, Wayne M. Itano, Dietrich G. Leibfried, David J. Wineland

Published Jun 7, 1996• 0 citations
OpenAlex

Abstract

Summary form only given. A quantum computer is composed of quantum bits that can support superposition states and hence allow parallel processing for certain problems such as factorization. All quantum computations can, in principle, be reduced to a series of two-bit quantum logic gates accompanied by simple single-bit rotations. An example of a two-bit quantum logic gate is the controlled-NOT (CN) gate, which rotates one quantum bit by 180 dependent on the state of a second quantum bit. We demonstrate operation of a two bit CN quantum logic gate on a trapped ion.

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•Jan 1, 2010•6 citations
Summary form only given. A quantum computer is composed of quantum bits that can support superposition states and hence allow parallel processing for certain problems such as factorization. All quantum computations can, in principle, be reduced to a series of two-bit quantum logic gates accompanied by simple single-bit rotations. An example of a two-bit quantum logic gate is the controlled-NOT (CN) gate, which rotates one quantum bit by 180 dependent on the state of a second quantum bit. We demonstrate operation of a two bit CN quantum logic gate on a trapped ion.
We show how to construct a multiqubit control gate on a quantum register of an arbitrary size N. This gate performs a single-qubit operation on a specific qubit conditioned by the state of other $N\ensuremath{-}1$ qubits. We provide an algorithm how to build up an array of networks consisting of single-qubit rotations and multiqubit control-NOT (CNOT) gates for the synthesis of an arbitrary entangled quantum state of N qubits. We illustrate the algorithm on a system of cold trapped ions. This example illuminates the efficiency of the direct implementation of the multiqubit CNOT gate compared to its decomposition into a network of two-qubit CNOT gates.
One of the fundamental tenets of quantum mechanics is the existence of superposition states, or states whose properties simultaneously possess two or more distinct values. Although quantum superpositions and entanglements seldom appear outside of the microscopic quantum world, there is growing interest in the creation of “big” superpositions and massively entangled states for use in applications such as a quantum computer.1 We report first steps toward this goal by demonstrating a fondamental two-bit quantum logic gate and a “Schrödinger cat”-like state of motion with a single trapped beryllium atom. Both experiments allow sensitive measurements of decoherence mechanisms which will play an important role in the feasibility of quantum computation.
The promise of tremendous computational power, coupled with the development of robust error-correcting schemes, has fuelled extensive efforts to build a quantum computer. The requirements for realizing such a device are confounding: scalable quantum bits (two-level quantum systems, or qubits) that can be well isolated from the environment, but also initialized, measured and made to undergo controllable interactions to implement a universal set of quantum logic gates. The usual set consists of single qubit rotations and a controlled-NOT (CNOT) gate, which flips the state of a target qubit conditional on the control qubit being in the state 1. Here we report an unambiguous experimental demonstration and comprehensive characterization of quantum CNOT operation in an optical system. We produce all four entangled Bell states as a function of only the input qubits' logical values, for a single operating condition of the gate. The gate is probabilistic (the qubits are destroyed upon failure), but with the addition of linear optical quantum non-demolition measurements, it is equivalent to the CNOT gate required for scalable all-optical quantum computation.
A quantum computer is a device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, the amount of data is measured by bits, in a quantum computer; it is measured by quantum of bits (qubits). This work describes, and implements the universal quantum logic gates, the terminology is introduced with two well known quantum gates, the quantum NOT, and the quantum XOR gates. The NOT and XOR gates have already been described in classical reversible logic. This work gives the implementation of the quantum circuits, such as the Quantum Half-Adder Circuits, which consists of quantum control control not gate (CCNot) and quantum control not gate (CNot). Also, it describes and implements the Quantum Full-Adder Circuits, which consists of two Quantum Half-Adder Circuits and one control not gate (CNot). Depending on the quantum circuits, one can implement the quantum basic arithmetic operations such as (addition, subtraction, multiplication and division). After each implementation, the computational complexity of each step is calculated. Key words: