- The New Quantum Age From Bells Theorem to Quantum Computation and Teleportatio | eBay
- 1. The achievements of twentieth century physics
- Quantum Information Applications Without Computers
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## The New Quantum Age From Bells Theorem to Quantum Computation and Teleportatio | eBay

Grangier, G. Dalibard, G. Faster than propagation of light between polarizers 40 ns and even than time of flight of photons between the source S and each switch 20 ns. Entanglement at a very large distance Geneva experiment : Optical fibers of the commercial telecom network Measurements separated by 30 km Agreement with QM. Innsbruck experiment : variable polarizers with orientation chosen by a random generator during the propagation of photons several hundreds meters.

Agreement with QM. Feynman , D. QKD at large distance, from space, on the agenda.

Fundamentally different hardware: fundamentally different software. What would be a quantum computer? Drastically different from concepts underlying the first quantum revolution wave particle duality.

### 1. The achievements of twentieth century physics

Individual quantum objects experimental control theoretical description quantum Monte-Carlo Examples: electrons, atoms, ions, single photons, photons pairs. The most likely roadmap as usual : from proofs of principle with well defined elementary microscopic objects photons, atoms, ions, molecules… to solid state devices and continuous variables? Single detections: No information about a Joint detections: Instantaneous change! Faster than light signaling? Joint detections: Instantaneous change!

Feynman: Simulating Physics with Computers, Int. Entanglement with more particles can lead even farther from classical concepts Understanding the extraordinary properties of entanglement has triggered a new research field: quantum information Hardware based on different physical principles can lead to new concepts in information theory: Quantum computing R. Using that key, Alice and Bob can exchange publicly a coded message with a mathematically proven safety Shannon theorem provided the message is not longer than the key Eve Alice Bob Quantum optics provides means of safe key distribution QKD.

Entangled Polarized Photons. Crystals can produce pairs of photons, heading in different directions. These pairs always show the same polarization. Experiments thought to prove non — locality may be artifacts Karl Otto Greulich. Fritz Lipmann Institute Beutenbergstr. Such super-sensitive atomic clocks help with GPS navigation, telecommunications and surveying. The precision of atomic clocks relies partially on the number of atoms used.

## Quantum Information Applications Without Computers

Kept in a vacuum chamber, each atom independently measures time and keeps an eye on the random local differences between itself and its neighbors. If scientists cram times more atoms into an atomic clock, it becomes 10 times more precise—but there is a limit on how many atoms you can squeeze in.

Entangled atoms would not be preoccupied with local differences and would instead solely measure the passage of time, effectively bringing them together as a single pendulum. That means adding times more atoms into an entangled clock would make it times more precise. Entangled clocks could even be linked to form a worldwide network that would measure time independent of location.

### Search results on physics.org

Traditional cryptography works using keys: A sender uses one key to encode information, and a recipient uses another to decode the message. This can be fixed using potentially unbreakable quantum key distribution QKD. In QKD, information about the key is sent via photons that have been randomly polarized. This restricts the photon so that it vibrates in only one plane—for example, up and down, or left to right.

The recipient can use polarized filters to decipher the key and then use a chosen algorithm to securely encrypt a message.

## The New Quantum Age

The secret data still gets sent over normal communication channels, but no one can decode the message unless they have the exact quantum key. That's tricky, because quantum rules dictate that "reading" the polarized photons will always change their states, and any attempt at eavesdropping will alert the communicators to a security breach. In Switzerland tried out an ID Quantique product to provide a tamper-proof voting system during an election. And the first bank transfer using entangled QKD went ahead in Austria in But this system doesn't yet work over large distances.

So far, entangled photons have been transmitted over a maximum distance of about 88 miles. A standard computer encodes information as a string of binary digits, or bits. Quantum computers supercharge processing power because they use quantum bits, or qubits, which exist in a superposition of states—until they are measured, qubits can be both "1" and "0" at the same time. This field is still in development, but there have been steps in the right direction.

The company says these are the world's first commercially available quantum computers. There's also uncertainty over whether the chips display any reliable quantum speedup. This type of microscope fires two beams of photons at a substance and measures the interference pattern created by the reflected beams—the pattern changes depending on whether they hit a flat or uneven surface.

Using entangled photons greatly increases the amount of information the microscope can gather, as measuring one entangled photon gives information about its partner.

The Hokkaido team managed to image an engraved "Q" that stood just 17 nanometers above the background with unprecedented sharpness. Similar techniques could be used to improve the resolution of astronomy tools called interferometers, which superimpose different waves of light to better analyze their properties. Interferometers are used in the hunt for extrasolar planets, to probe nearby stars and to search for ripples in spacetime called gravitational waves. Humans aren't the only ones making use of quantum mechanics.

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