Very true point.
With the launch of the world’s first quantum communication satellite, the era of unhackable communication has begun.
Category: quantum physics – Page 918
Quantum Entanglement: Slower Than Light
Although this is true (speed of communication via entanglement is not at the speed of light); like other early stage technologies this will also evolve and improve in time.
China recently launched a satellite to test quantum entanglement in space. It’s an interesting experiment that could lead to “hack proof” satellite communication. It’s also led to a flurry of articles claiming that quantum entanglement allows particles to communicate faster than light. Several science bloggers have noted why this is wrong, but it’s worth emphasizing again. Quantum entanglement does not allow faster than light communication.
This particular misconception is grounded in the way quantum theory is typically popularized. Quantum objects can be both particles and waves, They have a wavefunction that describes the probability of certain outcomes, and when you measure the object it “collapses” into a particular particle state. Unfortunately this Copenhagen interpretation of quantum theory glosses over much of the subtlety of quantum behavior, so when it’s applied to entanglement it seems a bit contradictory.
The most popular example of entanglement is known as the Einstein-Podolsky-Rosen (EPR) experiment. Take a system of two objects, such as photons such that their sum has a specific known outcome. Usually this is presented as their polarization or spin, such that the total must be zero. If one photon is measured to be in a +1 state, the other must be in a −1 state. Since the outcome of one photon affects the outcome of the other, the two are said to be entangled. Under the Copenhagen view, if the entangled photons are separated by a great distance (in principle, even light years apart) when you measure the state of one photon you immediately know the state of the other. In order for the wavefunction to collapse instantly the two particles must communicate faster than light, right? A popular counter-argument is that while the wavefunction does collapse faster than light (that is, it’s nonlocal) it can’t be used to send messages faster than light because the outcome is statistical.
Organic LEDs with low power consumption and long lifetimes
A novel device architecture is used to simultaneously achieve extremely high internal quantum efficiencies, low drive voltages, and long lifetimes, at practical luminance levels.
An LED with an emissive organic thin film sandwiched between the anode and cathode is known as an organic-LED (OLED). The emission mechanism of an OLED is superficially similar to that of a standard LED, i.e., holes and electrons are injected from the anode and cathode, respectively, and these carriers recombine to form excited states (excitons) that lead to light emission.1 In recent years, smartphones and TVs with OLED displays have rapidly become widespread because OLEDs provide high contrast, a wide color gamut, light weight, thinness, and flexibility for the displays. OLEDs also have great potential for the creation of new lighting applications.2 The high power consumption and short lifetime of OLEDs, however, remain key issues.
New single-photon microwave source developed
A collaboration including researchers at the National Physical Laboratory (NPL) has developed a tuneable, high-efficiency, single-photon microwave source. The technology has great potential for applications in quantum computing and quantum information technology, as well as in studying the fundamental reactions between light and matter in quantum circuits.
Circuits which produce single photons are a vital component in quantum computers. They usually consist of a quantum bit or ‘qubit’, coupled to a resonance circuit. The resonant circuit limits the photon output to specific frequencies depending on the design of the circuit.
Synopsis: Tickled by a Wigner Crystal
Nice synopsis.
The lattice symmetry of a quantum Wigner crystal is deduced from its effect on quantized states in a nearby sheet of electrons.
Left to their own devices, electrons confined to a sheet can crystallize into an ordered array at low temperatures because of their mutual repulsion. Physicists have observed a classical version of this “Wigner crystal” in electrons floating on liquid helium and a quantum variety in electrons trapped at a semiconductor interface. But the lattice geometry of electrons in the latter has been tough to glean. A team led by Mansour Shayegan at Princeton University, New Jersey, obtained this information using a new technique, possibly providing a way to test the many-body theories that predict Wigner crystallization.
The experimental device consists of a stack of two closely spaced semiconductor quantum wells. Electrons in quantum wells are effectively trapped in 2D, and at high magnetic fields and low temperatures they fall into quantized orbits. These states are the basis of the fractional quantum Hall effect (FQHE), whose signature is sharp dips in the resistance at fractional values of the so-called filling factor (the ratio of electron density to field strength).