Application: Quantum Computing

Is information physical? Computers process information. Computer scientist and physicist Rolf Landauer was a proponent of the idea that information is an aspect of the physical world. He elaborated this as follows: Information is not a disembodied abstract entity; it is always tied to...

Bell-Tests and the End of Local Realism

Can experiments probe the nature of reality? The year 2015 was a very good year for quantum theory, yet it was not such a good year for ‘classical reality.’ Since the inception of quantum theory in the 1920s, its implications regarding what can be...

Milestones and a Fork in the Road

What aspects of quantum physics have we seen so far, and what topics should we discuss next? We find ourselves at a fork in the road on the way to understanding quantum physics. In a historical progression, it would make sense next to discuss...

Application: Sensing Gravity with Quantum Interference

What is the technology of sensing? The human body has at least five senses: touch, taste, smell, sight, and hearing. A human sense is any biological process that generates a noticeable signal informing a person of a physical stimulus or condition. Each involves a...

Application: Sensing Time, Motion, and Gravity with Quantum Technology

What are quantum physics–based sensing technologies? Quantum physics–based sensing technologies are those that rely on quantum physics principles for their working. If classical physics were the whole story, we would not have access to these new technologies. In Chapter 5, I introduced...

Energy Quantization and Atoms

What is energy quantization in quantum mechanics? We now return to a more historical progression and discuss how Schrödinger’s equation describes the properties and behaviors of atoms, as was Schrödinger’s original motivation. This area of study is called quantum mechanics . A major idea...

Quantum Entanglement and Teleportation

What is quantum entanglement? Quantum entanglement is a characteristic of special quantum states describing two or more quantum entities, such as photons or electrons. It represents a form of measurement correlation that occurs only in quantum physics. Recall from Chapter 8 that...

Quantum Possibilities and Waves

How does the concept of waves enter quantum theory? In quantum theory, probabilities are determined by considering all the possibilities that may be involved in a certain process. If there are intermediate possibilities involved in a process, quantum theory tells us how to combine...

Quantum Physics

What is quantum physics? Quantum physics is the study of matter and energy—the basic constituents of the physical world—in the ‘quantum realm.’ The quantum realm encompasses those aspects of Nature that cannot be explained using classical physics. By ‘classical physics’ we physicists mean the...

Quantum Fields and Their Excitations

What are classical particles and fields? In a classical physics description of Nature, all elementary entities are considered to be either particles or fields. In this theory, a particle is an object that has mass—meaning it has inertia and is subject to...