1. Applications of Quantum Physics
In this presentation you will:
recognize examples of applications of quantum phenomena
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2. Introduction
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.
Their studies led to the recognition
that energy is emitted and absorbed
by 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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3. Electronics
Much of modern technology operates at a scale where quantum effects are significant.
The study of semiconductors led to the invention of the diode, the transistor, and the microprocessor, which are indispensable for modern electronics.
Other examples include the laser, the electron microscope, and magnetic resonance imaging.
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4. 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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5. Quantum Tunneling
Quantum tunnelling is vital in many electronic devices, being the basis for transistor operation.
Flash memory chips, found in USB drives, use quantum tunnelling to erase their memory cells.
electron wavepacket
electric field
The wave function of the electron encounters the electric field, but has some finite probability of tunneling through
Quantum Picture
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6. Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a form of medical imaging.
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.
Courtesy EFDA JET
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7. Lasers
Lasers work using the quantum phenomenon known as stimulated emission.
Incident photon hf
Ground energy level
Excited energy level
Before emission
Atom in excited state ∆E E2 E1
The electron of an atom is stimulated by an incident photon.
E2 - E1 = ∆E = hf
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8. Lasers
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.
Incident photon hf
Ground energy level
Excited energy level
Before emission
Atom in excited state ∆E E2 E1 hf
During emission hf
After emission
Atom in ground state
E2 - E1 = ∆E = hf
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9. Quantum Dots
Quantum dots are tiny particles of a semiconductor material, with a width of about 50 atoms.
By controlling the size of the dot, the light it emits or absorbs can be very precisely controlled.
Applications of quantum dots include the following:
Courtesy EFDA JET
Lighting
Solar cells
Light detectors
Security marking
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10. Spin
All elementary particles, such as protons, neutrons, and electrons, have a property called spin.
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. On
Off
The spin of an electron here is represented as up or down. Controlling the spin determines the state of the switch.
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11. Spin
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. On
Off
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12. Superconductivity
Superconductivity allows the creation of extremely powerful magnets, which can be used in Maglev train systems, MRI, and particle accelerators.
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.
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13. Superconductivity
With zero resistance, extremely large currents can flow in electromagnets without creating significant heating effects (I2 R).
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14. Digital Cameras
Modern digital cameras contain a light-sensing device rather than film.
Light hitting the light sensor produces a charge due to the photoelectric effect.
Light
An array of light sensors can be used to produce an image.
Solar panels also use a similar effect to create electricity from light.
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15. Nanotechnology
One of the ultimate applications will be nanotechnology.
Nanotechnology is the fabrication of structures and machines based on rearranging individual atoms. This occurs at a scale of nm, hence the name, and at this scale, the quantum effect is dominant.
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16. Nanotechnology
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.
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17. Question 1
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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18. Question 1
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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19. Question 2 Flash memory chips use which quantum phenomenon?
A) Superconductivity
B) Quantum tunneling
C) Electron spin
D) Stimulated emission
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20. Question 2 Flash memory chips use which quantum phenomenon?
A) Superconductivity
B) Quantum tunneling
C) Electron spin
D) Stimulated emission
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21. 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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22. 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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23. Summary In this presentation you have identified:
applications of quantum phenomena
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