Applications of Quantum Physics

In this presentation you will:

recognize examples of applications of quantum phenomena

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The foundations for many of the technological advances in our world today were laid by the scientists Max Planck and Albert Einstein early in the 20th century.

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Introduction

Their studies led to the recognition that energy is emitted and absorbedby atoms in discrete amounts – not in a linearly variable manner. This discovery of discrete energy quanta led to the study of quantum physics.

Progress in today’s world, full of microelectronic devices, is driven by this branch of science.

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Electronics

Much of modern technology operates at a scale where quantum effects are significant.

Other examples include the laser, the electron microscope, and magnetic resonance imaging.

The study of semiconductors led to the invention of the diode, the transistor, and the microprocessor, which are indispensable for modern electronics.

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Quantum Tunneling

Quantum tunneling refers to the phenomenon of a particle passing through a barrier that it should not be able to cross because its total mechanical energy is lower than the potential energy of the barrier.

electron electric field

The electron is repelled by an electric field as long as the energy of electron is below the energy level of the field

Classical Picture

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Quantum Tunneling

Quantum tunnelling is vital in many electronic devices, being the basis for transistor operation.

electron wavepacket electric field

The wave function of the electron encounters the electric field, but has some finite probability of tunneling through

Quantum Picture

Flash memory chips, found in USB drives, use quantum tunnelling to erase their memory cells.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a form of medical imaging.

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Courtesy EFDA JET

The MRI scanner has powerful magnets, which cause the protons of hydrogen atoms in water to align.An electromagnetic pulse is then produced by the machine that causes the protons to resonate.

The signal given off by the protons is processed and used to build up a picture.

Lasers

Lasers work using the quantum phenomenon known as stimulated emission.

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The electron of an atom is stimulated by an incident photon.

Incident photon

hf

Ground energy level

Excited energy level

Before emission

Atom in excited state

∆E

E2

E1

E2 - E1 = ∆E = hf

Lasers

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hf

During emission

hf

hf

After emission

Atom in ground state

Incident photon

hfGround

energy level

Excited energy level

Before emission

Atom in excited state

∆E

E2

E1

E2 - E1 = ∆E = hf

When the electron drops back to a lower energy level, it causes the electron to emit a photon that is in phase with the first.

This process goes on to stimulate other photons, and a cascade of identical photons builds up.

Quantum Dots

Quantum dots are tiny particles of a semiconductor material, with a width of about 50 atoms.

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Courtesy EFDA JET

Applications of quantum dots include the following:

By controlling the size of the dot, the light it emits or absorbs can be very precisely controlled.

Lighting

Solar cells

Light detectors

Security marking

The spin of an electron here is represented as up or down. Controlling the spin determines the state of the switch.

Spin

All elementary particles, such as protons, neutrons, and electrons, have a property called spin.

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If you think of a particle as a tiny solid ball, then spin is equivalent to the rotation of the particle about its own axis.

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Spin

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Electron spin plays an important role in magnetism, with applications in computer memories. The manipulation of nuclear spin by radio frequency waves is important in medical imaging.

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Superconductivity

Superconductivity is a property of a material that allows it to carry an electrical current with zero resistance and, therefore, no losses.Initially, this only occurred in materials at very low temperatures near 0 K. New ceramic materials are being developed that are superconductive at higher temperatures.

Superconductivity allows the creation of extremely powerful magnets, which can be used in Maglev train systems, MRI, and particle accelerators.

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Superconductivity

With zero resistance, extremely large currents can flow in electromagnets without creating significant heating effects (I2 R).

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Digital Cameras

Modern digital cameras contain a light-sensing device rather than film.

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Light hitting the light sensor produces a charge due to the photoelectric effect.

Solar panels also use a similar effect to create electricity from light.

Light

An array of light sensors can be used to produce an image.

Nanotechnology

One of the ultimate applications will be nanotechnology.

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Nanotechnology is the fabrication of structures and machines based on rearranging individual atoms. This occurs at a scale of 1 - 100 nm, hence the name, and at this scale, the quantum effect is dominant.

Nanotechnology

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Nanotechnology has many potential applications. Those currently under research include machines able to travel inside blood vessels and deliver drugs to specific parts of the body.

Which application uses the quantum principle of stimulated emission?

A) Flash memory chips

B) MRI scanners

C) Lasers

D) Maglev trains

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Question 1

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Question 1

Which application uses the quantum principle of stimulated emission?

A) Flash memory chips

B) MRI scanners

C) Lasers

D) Maglev trains

Flash memory chips use which quantum phenomenon?

A) Superconductivity

B) Quantum tunneling

C) Electron spin

D) Stimulated emission

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Question 2

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Question 2

Flash memory chips use which quantum phenomenon?

A) Superconductivity

B) Quantum tunneling

C) Electron spin

D) Stimulated emission

Question 3

Powerful magnets are possible through which quantum phenomenon?

A) Superconductivity

B) Quantum tunneling

C) Electron spin

D) Stimulated emission

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Question 3

Powerful magnets are possible through which quantum phenomenon?

A) Superconductivity

B) Quantum tunneling

C) Electron spin

D) Stimulated emission

applications of quantum phenomena

In this presentation you have identified:

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Summary