Last week, I participated in Quantum Sensing Linz, a small-scale conference on Quantum Sensing. Since my own work centers mostly on Quantum Software Engineering, the conference was a great opportunity to broaden my horizons and realize once again how little I actually know. But let’s start at the beginning. What Read more…
In the quantum circuit model of quantum computing, we represent a quantum program as a sequence of gates, where each gate is an operation that changes the state of the system. Although easy to visualize and interpret, this representation of a circuit as a sequence of gates is not unique. Read more…
Probability amplitudes and phase As mentioned in What is Quantum Interference?, until the system is measured, each state in the superposition of a quantum system has an associated probability amplitude. In the case of electron spin, for example, a single electron has two associated probability amplitudes, one for each spin Read more…
If quantum particles sometimes behave as waves (see the double slit experiment for more details) it’s fair to expect wave-like phenomena play a role in quantum physics and, hence, in quantum computing. (Quantum) Interference is such a phenomenon. It builds on our notion of Superposition and helps us understand why Read more…
With Entanglement, Quantum Superposition is one of the cornerstones of quantum computing. It forms the basis of all quantum algorithms and is the main reason quantum computers can outperform classical computers on certain problems. In this article, you will learn the origin of Superposition in the context of quantum mechanics, Read more…
The Quantum Fourier Transform (QFT) is one of the most popular and widely used quantum algorithms today. It is part of many other quantum algorithms, including Quantum Phase Estimation and Shor’s Algorithm, and can be seen as a quantum version of the Discrete Fourier Transform (DFT). While it is easy Read more…
How does Grover’s Algorithm work? Grover’s Algorithm is one of the most popular quantum algorithms. While it does not achieve the exponential speedup of Shor’s algorithm, it enables the user to find an entry in an unsorted list of N elements in only steps. The application areas of the algorithm Read more…
What is Phase Kickback? Phase Kickback is a building block of many popular quantum algorithms, including Deutsch’s Algorithm, Quantum Phase Estimation, and Shor’s Algorithm for integer factorization. It is built on the mathematical notion of eigenvalues and eigenstates and enables us to reverse the chain of cause and effect (to Read more…
Can a single qubit store infinite information? Qubits are to quantum computing what bits are for classical (non-quantum) computing: they form the basic unit of computation and determine how data can be stored and manipulated in a computer. While each classical bit can store a value of 0 or 1, Read more…
How does Deutsch’s Algorithm work? In 1985, David Deutsch devised an algorithm to illustrate a situation in which a quantum computer can outperform any classical computer in the amount of required (quantum) oracle calls. While the algorithm itself shows little real-world applicability, it serves as a fascinating case study illustrating Read more…
Entanglement and Superposition are the basis of what makes quantum computers different from classical computers and causes their incredible performance gains. In this article, you will learn in a jargon-free way what entanglement is and where it comes from. What is Entanglement? Let’s imagine for a second that you have Read more…
Is Quantum Computing really parallel? This is one of those apparently simple questions that really made my head spin when I first learned about quantum computing. Many articles on the web claim that quantum computers can run high numbers of computations in parallel, solving problems in mere hours that would Read more…
Why I started this blog “Everything should be made as simple as possible, but not simpler.” (Albert Einstein) When I first learned about quantum computing while preparing for my thesis, this was an issue. Having a brain that wants to understand things before applying them, I found myself lost in Read more…