Superconducting Qubits RIKEN | UBC | Sherbrooke – In arXiv 0805.0164, Zagoskin and Blais provide a broad and accessible introduction to quantum information processing with superconducting qubits. "From a physicist's standpoint, the most interesting part of quantum computing research may well be the possibility to probe the boundary between the quantum and the classical worlds. The more macroscopic are the structures involved, the better. So far, the most "macroscopic" qubit prototypes that have been studied in the laboratory are certain kinds of superconducting qubits. To get a feeling for how macroscopic these systems can be, the states of flux qubits which are brought in a quantum superposition corresponds to currents composed of as much as 10⁵ - 10⁶ electrons flowing in opposite directions in a superconducting loop."

Efficient pulsed gates for an oscillator stabilized Josephson qubit IBM Watson In arXiv 0709.1478 and New J. Phys. 10 033027 (2008), Koch, DiVincenzo, Brito and Steffen derive operational specifications for high-fidelity one and two-qubit pulsed gates for a superconducting flux qubit, calculating the Hamiltonian with tunable interaction from initialization to readout.

"The quantitative fact that the values of gate infidelity are at the 1% level – and below – is the major result of this paper."

So, can a "debugged" IBM qubit be used soon for universal quantum computation?

"The short answer is, in our opinion, ultimately yes."

"The answer would certainly be no if the noise threshold for fault-tolerant quantum computation were in the neighborhood of the oft-quoted value of 10⁻⁵. It is not inconceivable for the experiment to get to these values someday, since we find that the infidelities decrease much faster than linearly with the assumed noise levels."

"To get to 10⁻⁵, we would need to get to the very daunting levels of 100nΦ₀ at 1Hz for the 1/f noise amplitudes and 100 f s for timing accuracies; there is optimism that both of these numbers are ultimately attainable. Fortunately, while 10⁻⁵ was the threshold as it was understood ten years ago, much recent work shows that with good designs, much higher thresholds are possible. According to Terhal and Burkard – 1% is, in fact, on the high end of the noise levels for which fault tolerance may be possible."

Photon transmission through sub-wavelength diameter apertures Delft | Optica In Optics Express 16, 10 (abstract, full article) and concurrent TU Delft summary, Photonics review, Adam, Planken et al. report on high time-resolution terahertz mapping of photon transmission through sub-wavelength diameter apertures:

"According to the laws of physics, it is particularly difficult to pass light through a hole smaller than half the wavelength of the light used." The Delft group conducted experiments using extremely high time-resolution measurements in the terahertz (THz) frequency range. The group discovered that even if the hole is up to fifty times smaller than the wavelength used, sufficient light can pass through to allow measurements near the hole – an extremely difficult task using other methods. "Improving the sharpness of THz microscopes, coupled with more sensitive detectors, will improve the viability of creating images of biological cells using this type of measurement."

Prior experiments at Leiden University (Nature 418, 304-306) have also studied photon transmission through sub-wavelength metal films and shown entanglement conservation to be much more robust than expected – surviving the conversion process from surface-plasmon waves, which tunnel through the barrier, before reradiating as photons on the opposite side of the film. "It's a good omen, because it's saying quantum entanglement can survive when you might not expect it to," says Bill Barnes, a photonics expert at the University of Exeter. "If they can survive this, what else can they survive?"

Time Reversal in Bose-Einstein Condensates Toulouse | CNRS In arXiv 0804.3514, Martin, Georgeot, and Shepelyansky of Quantware MIPS Center investigate time reversibility in Bose-Einstein condensates (BEC). "We show that inside the regime of quantum chaos, time-reversal dynamics can be inverted from explosion to collapse. The accuracy of time reversal decreases with the increase of atom interactions inside BEC, until it is completely lost – though, surprisingly, quantum chaos helps to restore time reversibility. Existing experimental setups similar to Ryu, Behinaein, and Wayper can test the fundamental question of BEC time reversal discussed here."

DARPA INFOSEC Mandate DARPA | EOP | Congress In Wired briefing 01 May 2008, Danger Room reports on the new DARPA Information Security program mandated by Congress and ratified by the President. The UNISCA First Committee INFOSEC Chair briefing to the UN General Assembly is particularly àpropos to the initiative. "The Defense Advanced Research Projects Agency, or DARPA, was created 50 years ago in response to the Soviets' launch of Sputnik. In less than a year, DARPA put together the infrastructure that guided the American space effort for decades to come. Now, DARPA has been given new marching orders: to help America fight and win battles online.

Under a directive signed by the President – and recently approved by Congress – nearly every arm of the government's security apparatus is starting work on a massive national cybersecurity initiative designed to protect the United States from electronic attack and strike at adversaries online. DARPA's role: to create a cyberwarfare range where all these new forms of electronic combat can be tried out. According to a defense official familiar with the program, "Congress has given DARPA a direct order; that's only happened once before – with the Sputnik program in the '50s."

Danger Room's sister blog, Threat Level, has a good writeup of the cybersecurity initiative, which has been labeled as a Manhattan Project-type effort. In the case of cybersecurity, there is at least talk of big money: about $30 billion dollars. For its part, DARPA's "National Cyber Range" would create a virtual environment where the Defense Department can mock real warfare, both defense and offense.

DARPA today issued an announcement, describing how the range would be a test where the government could conduct unbiased, quantitative and qualitative assessment of information assurance and survivability tools in a representative network environment ; replicate complex, large-scale, heterogeneous networks and users in current and future Department of Defense (DoD) weapon systems and operations ; enable multiple, independent, simultaneous experiments on the same infrastructure ; enable realistic testing of Internet/Global-Information-Grid (GIG) scale research ; develop and deploy revolutionary cyber testing capabilities, and enable the use of the scientific method for rigorous cyber testing.

This is clearly a serious deal for the agency: DARPA Director Tony Tether is a scheduled speaker at the proposers' day workshop scheduled for mid-May, and apparently plans to help handpick the contractors. Tether is known for his close involvement in DARPA contracts. Many of the details surrounding this program will be classified."

Quantum sensor effect in bird navigation? Institute for Electronic Structure and Lasers, Foundation for Research and Technology, Heraklion | University of Crete In arXiv:0804.2646, arXivblog, and Slashdot reports, Kominis investigates the potential for Zeno effect-based quantum sensing in bird navigation. "How birds use the Earth's magnetic field to navigate has puzzled researchers for decades. In recent years, a growing body of evidence has pointed to the possibility that a weak magnetic field can influence the outcome of a certain type of chemical reaction involving the recombination of pairs of ions in bird retinas. The trouble is that the ion recombination is known to happen too quickly for the Earth's weak magnetic field to have any effect. Now it looks as if the quantum Zeno effect may explain the process (abstract). This is the "watched-pot-never-boils" effect, in which the act of observing a quantum system maintains it for longer than expected. This is extraordinary news, because it means a quantum sensor is determining the macroscopic behavior of living birds. Kominis says we may well see these effects elsewhere, and mentions that a similar mechanism might be at work in photosynthesis."

MagiQ Research Labs Andrew Hammond | MagiQ Technologies MagiQ Technologies (NYC) has founded MagiQ Research Labs in Somerville, MA. The lab will provide a technical, engineering and production facility base for public and private sectors in medical optics, quantum information, fiber sensing, aerospace and defense applications, and has been established under research grants from ARO, DARPA, and NASA.

Room-temperature quantum oscillations in diamond crystals UCSB|CNSI|Kavli TU Delft|Ames DOE In Science Express, Science and concurrent UCSB press release, Hanson, Awschalom et al. report on striking experimental observations of quantum oscillations in diamond crystals at room temperature. "We were stunned by these unexpected experimental results, and extremely excited by the ability to control and monitor single quantum states, especially at room temperature," said David Awshalom. "To our surprise, when looking at longer times, the oscillations disappeared, then re-appeared. At first it looked like an artifact, but repeated measurements reproduced this behavior," said co-author Ronald Hanson, a postdoctoral student at UCSB during this period who is now a professor at Kavli Institute of Nanoscience Delft, Delft University of Technology, in the Netherlands.