Introductory Quantum Algorithms

2006 ◽  
Author(s):  
Phillip Kaye ◽  
Raymond Laflamme ◽  
Michele Mosca
Keyword(s):  
Quantum Computation ◽  
Quantum Algorithms ◽  
The State ◽  
Second Step ◽  
Total Probability ◽  
Probabilistic Algorithms ◽  
Probabilistic Computation ◽  
Computation Path

In this chapter we will describe some of the early quantum algorithms. These algorithms are simple and illustrate the main ingredients behind the more useful and powerful quantum algorithms we describe in the subsequent chapters. Since quantum algorithms share some features with classical probabilistic algorithms, we will start with a comparison of the two algorithmic paradigms. Classical probabilistic algorithms were introduced in Chapter 1. In this section we will see how quantum computation can be viewed as a generalization of probabilistic computation. We begin by considering a simple probabilistic computation. Figure 6.1 illustrates the first two steps of such a computation on a register that can be in one of the four states, labelled by the integers 0, 1, 2, and 3. Initially the register is in the state 0. After the first step of the computation, the register is in the state j with probability p0,j . For example, the probability that the computation is in state 2 after the first step is p0,2. In the second step of the computation, the register goes from state j to state k with probability qj,k. For example, in the second step the computation proceeds from state 2 to state 3 with probability q2,3. Suppose we want to find the total probability that the computation ends up in state 3 after the second step. This is calculated by first determining the probability associated with each computation ‘path’ that could end up at the state 3, and then by adding the probabilities for all such paths. There are four computation paths that can leave the computation in state 3 after the first step. The computation can proceed from state 0 to state j and then from state j to state 3, for any of the four j ∊ {0, 1, 2, 3}. The probability associated with any one of these paths is obtained by multiplying the probability p0,j of the transition from state 0 to state j, with the probability qj,3 of the transition from state j to state 3.

scholarly journals Roots of quantum computing supremacy: superposition, entanglement, or complementarity?

2021 ◽  
Author(s):  
Andrei Khrennikov
Keyword(s):  
Quantum Computing ◽  
Quantum Algorithms ◽  
Probability Distributions ◽  
Statistical Tests ◽  
Joint Probability ◽  
Quantum Probability ◽  
Quantum Nonlocality ◽  
Total Probability ◽  
Probabilistic Algorithms ◽  
Quantum Phenomena

AbstractThe recent claim of Google to have brought forth a breakthrough in quantum computing represents a major impetus to further analyze the foundations for any claims of superiority regarding quantum algorithms. This note attempts to present a conceptual step in this direction. I start with a critical analysis of what is commonly referred to as entanglement and quantum nonlocality and whether or not these concepts may be the basis of quantum superiority. Bell-type experiments are then interpreted as statistical tests of Bohr’s principle of complementarity (PCOM), which is, thus, given a foothold within the area of quantum informatics and computation. PCOM implies (by its connection to probability) that probabilistic algorithms may proceed without the knowledge of joint probability distributions (jpds). The computation of jpds is exponentially time consuming. Consequently, classical probabilistic algorithms, involving the computation of jpds for n random variables, can be outperformed by quantum algorithms (for large values of n). Quantum probability theory (QPT) modifies the classical formula for the total probability (FTP). Inference based on the quantum version of FTP leads to a constructive interference that increases the probability of some events and reduces that of others. The physical realization of this probabilistic advantage is based on the discreteness of quantum phenomena (as opposed to the continuity of classical phenomena).

scholarly journals Roots of Quantum Computational Supremacy: Superposition? Entanglement? Or Complementarity?

2019 ◽  
Author(s):  
Andrei Khrennikov
Keyword(s):  
Measurement Problem ◽  
Quantum Algorithms ◽  
Statistical Tests ◽  
Joint Probability ◽  
Basic Feature ◽  
Quantum Nonlocality ◽  
Joint Probability Distribution ◽  
Total Probability ◽  
Probabilistic Algorithms ◽  
Quantum Superposition

The recent Google’s claim on breakthrough in quantum computing is a gong signal for further analysis of foundational roots of (possible) superiority of some quantum algorithms over the corresponding classical algorithms. This note is a step in this direction. We start with critical analysis of rather common reference to entanglement and quantum nonlocality as the basic sources of quantum superiority. We elevate the role of the Bohr’s principle of complementarity1 (PCOM) by interpreting the Bell-experiments as statistical tests of this principle. (Our analysis also includes comparison of classical vs genuine quantum entanglements.) After a brief presentation of PCOM and endowing it with the information interpretation, we analyze its computational counterpart. The main implication of PCOM is that by using the quantum representation of probability, one need not compute the joint probability distribution (jpd) for observables involved in the process of computation. Jpd’s calculation is exponentially time consuming. Consequently, classical probabilistic algorithms involving calculation of jpd for n random variables can be over-performed by quantum algorithms (for big values of n). Quantum algorithms are based on quantum probability calculus. It is crucial that the latter modifies the classical formula of total probability (FTP). Probability inference based on the quantum version of FTP leads to constructive interference of probabilities increasing probabilities of some events. We also stress the role the basic feature of the genuine quantum superposition comparing with the classical wave superposition: generation of discrete events in measurements on superposition states. Finally, the problem of superiority of quantum computations is coupled with the quantum measurement problem and linearity of dynamics of the quantum state update.

The Challenge of Mass Democracy

2018 ◽  
Author(s):  
Benjamin A. Schupmann
Keyword(s):  
Nineteenth Century ◽  
Liberal Democracy ◽  
The State ◽  
Parliamentary Democracy ◽  
The People ◽  
State And Society ◽  
Mass Democracy

Chapter 1 analyzes Schmitt’s assessment of democratic movements in Weimar and the gravity of their effects on the state and constitution. It emphasizes that the focus of Schmitt’s criticism of Weimar was mass democracy rather than liberalism. Schmitt warned that the combination of mass democracy, the interpenetration of state and society, and the emergence of total movements opposed to liberal democracy, namely the Nazis and the Communists, were destabilizing the Weimar state and constitution. Weimar, Schmitt argued, had been designed according to nineteenth century principles of legitimacy and understandings of the people. Under the pressure of mass democracy, the state was buckling and cannibalizing itself and its constitution. Despite this, Schmitt argued, Weimar jurists’ theoretical commitments left them largely unable to recognize the scope of what was occurring. Schmitt’s criticism of Weimar democracy was intended to raise awareness of how parliamentary democracy could be turned against the state and constitution.

scholarly journals A Two-Step State Estimation Algorithm for Hybrid AC-DC Distribution Grids

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1967
Author(s):  
Gaurav Kumar Roy ◽  
Marco Pau ◽  
Ferdinanda Ponci ◽  
Antonello Monti
Keyword(s):  
State Estimation ◽  
Distribution System ◽  
Renewable Energy Sources ◽  
Estimation Algorithm ◽  
The State ◽  
Second Step ◽  
Distribution Grid ◽  
Dc Distribution ◽  
Attractive Option ◽  
Distribution Grids

Direct Current (DC) grids are considered an attractive option for integrating high shares of renewable energy sources in the electrical distribution grid. Hence, in the future, Alternating Current (AC) and DC systems could be interconnected to form hybrid AC-DC distribution grids. This paper presents a two-step state estimation formulation for the monitoring of hybrid AC-DC grids. In the first step, state estimation is executed independently for the AC and DC areas of the distribution system. The second step refines the estimation results by exchanging boundary quantities at the AC-DC converters. To this purpose, the modulation index and phase angle control of the AC-DC converters are integrated into the second step of the proposed state estimation formulation. This allows providing additional inputs to the state estimation algorithm, which eventually leads to improve the accuracy of the state estimation results. Simulations on a sample AC-DC distribution grid are performed to highlight the benefits resulting from the integration of these converter control parameters for the estimation of both the AC and DC grid quantities.

Efficient linear optics quantum computation

2001 ◽  
Vol 1 (Special) ◽  
pp. 13-19
Author(s):  
G.J. Milburn ◽  
T. Ralph ◽  
A. White ◽  
E. Knill ◽  
R. Laflamme
Keyword(s):  
Quantum Computation ◽  
Single Photon ◽  
Quantum Algorithms ◽  
Optical Nonlinearities ◽  
Linear Optics ◽  
Optical Elements ◽  
Particle Detectors ◽  
Feed Forward ◽  
Single Electrons ◽  
Photon Source

Two qubit gates for photons are generally thought to require exotic materials with huge optical nonlinearities. We show here that, if we accept two qubit gates that only work conditionally, single photon sources, passive linear optics and particle detectors are sufficient for implementing reliable quantum algorithms. The conditional nature of the gates requires feed-forward from the detectors to the optical elements. Without feed forward, non-deterministic quantum computation is possible. We discuss one proposed single photon source based on the surface acoustic wave guiding of single electrons.

scholarly journals The Jones polynomial: quantum algorithms and applications in quantum complexity theory

2008 ◽  
Vol 8 (1&2) ◽  
pp. 147-180
Author(s):  
P. Wocjan ◽  
J. Yard
Keyword(s):  
Quantum Computation ◽  
Braid Group ◽  
Quantum Algorithms ◽  
Primitive Root ◽  
Jones Polynomial ◽  
Tutte Polynomial ◽  
Roots Of Unity ◽  
Complete Problems ◽  
Primitive Roots ◽  
Quantum Complexity

We analyze relationships between quantum computation and a family of generalizations of the Jones polynomial. Extending recent work by Aharonov et al., we give efficient quantum circuits for implementing the unitary Jones-Wenzl representations of the braid group. We use these to provide new quantum algorithms for approximately evaluating a family of specializations of the HOMFLYPT two-variable polynomial of trace closures of braids. We also give algorithms for approximating the Jones polynomial of a general class of closures of braids at roots of unity. Next we provide a self-contained proof of a result of Freedman et al.\ that any quantum computation can be replaced by an additive approximation of the Jones polynomial, evaluated at almost any primitive root of unity. Our proof encodes two-qubit unitaries into the rectangular representation of the eight-strand braid group. We then give QCMA-complete and PSPACE-complete problems which are based on braids. We conclude with direct proofs that evaluating the Jones polynomial of the plat closure at most primitive roots of unity is a \#P-hard problem, while learning its most significant bit is PP-hard, circumventing the usual route through the Tutte polynomial and graph coloring.

Japan in the 1950s: Symbolic Victims

Alegal ◽  
2018 ◽  
pp. 15-37
Author(s):  
Annmaria M. Shimabuku
Keyword(s):  
Middle Class ◽  
Interwar Period ◽  
Mixed Race ◽  
The State ◽  
Sexual Slavery ◽  
Cultural Productions ◽  
Imperial Period ◽  
The Family ◽  
Sexual Labor

Chapter 1 presents a genealogy of sexual labor in Japan from licensed prostitution and the so-called “comfort woman” system of sexual slavery in the imperial period, through the state-organized system of prostitution for the Allied forces in the immediate postwar, and to the full-fledged emergence of independent streetwalkers thereafter. It links protest against private prostitution in the interwar period to aversion toward the streetwalker in the postwar period through an examination of Tosaka Jun’s Japanese Ideology. There, he defined Japanism as the symbolic communion between the family and state and showed how Japanists attacked private prostitution for purportedly interfering with the integrity of both. What was at stake was the ability of a budding middle class to manage the reproduction of labor power for the biopolitical state. Through Tosaka, this chapter delineates a mechanism of social defence amongst the middle class that targeted life thought to be unintelligible to the state such as the streetwalker and her mixed-race offspring. Further, it shows how this occurred through cultural productions such as anti-base reportage that focused obsessively on the figure of the streetwalker.

Quantum Algorithms

2021 ◽  
pp. 82-101
Author(s):  
Renata Wong ◽  
Amandeep Singh Bhatia
Keyword(s):  
Quantum Computing ◽  
Fault Tolerance ◽  
Quantum Computation ◽  
Quantum Computer ◽  
Quantum Algorithms ◽  
Computer Hardware ◽  
Quantum Mechanical ◽  
Computational Power ◽  
Quantum Devices ◽  
The Core

In the last two decades, the interest in quantum computation has increased significantly among research communities. Quantum computing is the field that investigates the computational power and other properties of computers on the basis of the underlying quantum-mechanical principles. The main purpose is to find quantum algorithms that are significantly faster than any existing classical algorithms solving the same problem. While the quantum computers currently freely available to wider public count no more than two dozens of qubits, and most recently developed quantum devices offer some 50-60 qubits, quantum computer hardware is expected to grow in terms of qubit counts, fault tolerance, and resistance to decoherence. The main objective of this chapter is to present an introduction to the core quantum computing algorithms developed thus far for the field of cryptography.

Sign in / Sign up

Export Citation Format

Share Document