Items tagged with "quantum dots"
This story was prepared by the Delft University of Technology (TU Delft) and adapted with permission. The experiments described were performed at TU Delft, with theoretical and numerical contributions from JQI Fellow and Condensed Matter Theory Center Director Sankar Das Sarma and JQI postdoctoral researcher Xiao Li.
From credit card numbers to bank account information, we transmit sensitive digital information over the internet every day. Since the 1990s, though, researchers have known that quantum computers threaten to disrupt the security of these transactions.
That’s because quantum physics predicts that these computers could do some calculations far faster than their conventional counterparts. This would let a quantum computer crack a common internet security system called public key cryptography.
Scientists have created a crystal structure that boosts the interaction between tiny bursts of light and individual electrons, an advance that could be a significant step toward establishing quantum networks in the future.
Researchers from JQI and Princeton University have built a rice grain-sized microwave laser, or "maser," powered by single electrons that demonstrates the fundamental interactions between light and moving electrons.
Quantum dots (QD) can be made from tiny crystals of semiconductor material, around 10 nanometers in size. The electron hole pairs in this structure are confined, resulting in a quantization of energy levels analogous to those of an atom – hence quantum dots are often dubbed ‘artificial atoms.’ Like an atom, a QD’s energy levels can be manipulated using lasers and magnetic fields. The fluorescing wavelengths can be tuned by altering the crystal size. Semiconductor quantum dots are attractive for quantum information processing because the technology for integration with modern electronics already exists. Read more to learn more about these artificial atoms.
Unfortunately, qubits are fragile; they dissipate in the face of interactions with their environment. A new JQI semiconductor-based qubit design ably addresses this issue of qubit robustness.
A JQI-theory/TU Delft-experimental collaboration has recently published results that could be used to rapidly and reliably reset a qubit stored in a semiconductor double quantum dot.
Quantum dots are effectively “artificial atoms.” They are nanocrystals of semiconductor wherein an electron-hole pair can be trapped. The nanometer size is comparable to the wavelength of light and so, just like in an atom, the electron can occupy discrete energy levels. The dots can be confined in a photonic crystal cavity, where they can be probed with laser light.
All computers, even the future quantum versions, use logic operations or “gates,” which are the fundamental building blocks of computational processes. JQI scientists, led by Professor Edo Waks, have performed an ultrafast logic gate on a photon, using a semiconductor quantum dot.
Photonic crystals (PCs) are extremely small structures, typically no more than a few micrometers on a side, which are made of alternating regions of insulating material and air. One way this can be achieved is by drilling or etching holes in the material at regular intervals in a grid pattern. A beam of photons passing through a PC thus experiences periodic changes in refractive index – high in the insulator, low in the air holes.