In my previous post on superconducting qubits, we have seen how a flux qubit represents a qubits state as a superposition of currents in a superconducting loop. Even though flux qubits have been implemented and used successfully, most research groups today focus on different types of qubits using a charge qubit as an archetype. Charge … Continue reading Superconducting qubits – on islands, charge qubits and the transmon

# Category: Quantum computing

# Superconducting qubits – the flux qubit

In the last post, we have discussed the basic idea of superconducting qubits - implement circuits in which a supercurrent flows that can be described by a quantum mechanical wave function, and use two energy levels of the resulting quantum system as a qubit. Today, we will look in some more detail into one possible … Continue reading Superconducting qubits – the flux qubit

# Superconducting qubits – an introduction

In some of the last posts in my series on quantum computing, we have discussed how NMR (nuclear magnetic resonance) technology can be used to implement quantum computers. Over the last couple of years, however, a different technology has attracted significantly more interest and invest - superconducting qubits. What are superconducting qubits? To start with … Continue reading Superconducting qubits – an introduction

# Quantum teleportation

Quantum states are in many ways different from information stored in classical systems - quantum states cannot be cloned and quantum information cannot be erased. However, it turns out that quantum information can be transmitted and replicated by combining a quantum channel and a classical channel - a process known as quantum teleportation. Bell states … Continue reading Quantum teleportation

# NMR based quantum computing: gates and state preparation

In my last post on NMR based quantum computing, we have seen how an individual qubit can be implemented based on NMR technology. However, just having a single qubit is of course not really helpful - what we are still missing is the ability to initialize several qubits and to realize interacting quantum gates. These … Continue reading NMR based quantum computing: gates and state preparation

# Single qubit NMR based quantum computation

In the previous post, we have sketched the basic ideas behind NMR based quantum computation. In this post, we will discuss single qubits and single qubit operations in more depth. The rotating frame of reference In NMR based quantum computing, quantum gates are realized by applying oscillating magnetic fields to our probe. As an oscillating … Continue reading Single qubit NMR based quantum computation

# Bulk quantum computing with nuclear spin systems

The theoretical foundations of universal quantum computing were essentially developed in the nineties of the last century, when the first native quantum algorithms and quantum error correction were discovered. Since then, physicists and computer scientists have been working on physical implementations of quantum computing. One of the first options that moved into the focus was … Continue reading Bulk quantum computing with nuclear spin systems

# Quantum error correction: the surface code

In my previous post on quantum error correction, we have looked at the toric code which is designed for a rather theoretical case - a grid of qubits on a torus. In reality, qubits are more likely to be arranged in a planar geometry. Luckily, a version of the toric codes that works well in … Continue reading Quantum error correction: the surface code

# Quantum error correction: an introduction to toric codes

While playing with the IBM Q experience in some of my recent posts, we have seen that real qubits are subject to geometric restrictions - two-qubit gates cannot involve arbitrary qubits, but only qubits that are in some sense neighbors. This suggests that efficient error correction codes need to tie to the geometry of the … Continue reading Quantum error correction: an introduction to toric codes

# Factoring integers on a quantum computer with Qiskit

After all the work done in the previous posts, we are now ready to actually implement Shor's factoring algorithm on a real quantum computer, using once more IBMs Q Experience and the Qiskit framework. First, recall that Shor's algorithm is designed to factor an integer M, with the restriction that M is supposed to be … Continue reading Factoring integers on a quantum computer with Qiskit