Monday, December 12, 2011

Tuesday, November 15, 2011

Q & A with Seth Lloyd

Here's a short question and answer with Seth Lloyd of MIT in Popular Science. As one would expect, this is more of a primer being in PopSci.

Saturday, August 27, 2011

Maintaining Entanglement for an Hour

Maintaining quantum states for any length of time is one of the big challenges in quantum computing. So this news about maintaining entanglement for an hour is encouraging. (Image from the article.)

Monday, July 25, 2011

Suppressing decoherence

Some progress towards suppressing decoherence, a major stumbling block towards physical implementations of quantum computers.

Saturday, July 16, 2011

Dave Bacon Moves to Google

I came across this: Dave Bacon, previously at the University of Washington, has moved on to Google. Is the commercialization of quantum computing on the horizon?

Michael Nielsen on Open Science

Michael Nielsen of [1] fame on open science:

[1] Nielsen, Michael A., and Isaac L. Chuang. Quantum Computation and Quantum Information. 2008. 1 ed. Cambridge, UK: Cambridge University Press, 2000. 8.

Tuesday, June 28, 2011

Wednesday, June 22, 2011

Paper: Verification of Quantum Programs

I'm of the opinion that formal verification of programs has a limited set of applications, in large part due to the "good enough" software principle. Nonetheless, it is nice to see work in the quantum programming area. Here's a just posted paper on arXiv: Verification of Quantum Programs by Ying, Yu, Feng, and Duan.

Monday, June 6, 2011

Cooling through computation

Erasing data generates heat. For example, an And gate can erase data because if you get a false (0) you don't know if the inputs were both false or if just one of them were 0. Hence quantum computers need to perform reversible operations. Here is some pretty cool work on cooling computers by the computations they perform.

Wednesday, June 1, 2011

D-Wave sells quantum computer to Lockheed Martin

For those who have not seen it yet, D-Wave has sold its first quantum computer to Lockheed Martin for 10 million. Here are a few of the many articles about it:

Wednesday, May 18, 2011

Verdal on the cover of the new Scientific American

Vlatko Verdal, of [1] fame, wrote an article titled "Living in a Quantum World", which made the cover of this month's (June 2011) cover of Scientific American.

[1] Vedral, Vlatko. Introduction to Quantum Information Science. 1 ed. Oxford, Great Britain: Oxford University Press, 2006.

More D-Wave Claims

For those who have not seen it yet, D-Wave is making some new claims. I've been skeptical since 2007, and still feel the same way. I think Scott Aaronson described the situation well in his blog, as he usually does about D-Wave.

Thursday, March 24, 2011

Quantum Public Key Encryption

One of the most cited benefits of a quantum computer is that it can factor, therefore breaking many current public key encryption systems. That makes this recent paper by Kawachi, Koshiba, Nishimura, and Yamakami certainly interesting: a quantum version of public key encryption. Here's a brief article in MIT Technology Review, and the paper on arXiv. The abstract:
We introduce a computational problem of distinguishing between two specific quantum states as a new cryptographic problem to design a quantum cryptographic scheme that is "secure" against any polynomial-time quantum adversary. Our problem, QSCDff, is to distinguish between two types of random coset states with a hidden permutation over the symmetric group of finite degree. This naturally generalizes the commonly-used distinction problem between two probability distributions in computational cryptography. As our major contribution, we show that QSCDff has three properties of cryptographic interest: (i) QSCDff has a trapdoor; (ii) the average-case hardness of QSCDff coincides with its worst-case hardness; and (iii) QSCDff is computationally at least as hard as the graph automorphism problem in the worst case. These cryptographic properties enable us to construct a quantum public-key cryptosystem, which is likely to withstand any chosen plaintext attack of a polynomial-time quantum adversary. We further discuss a generalization of QSCDff, called QSCDcyc, and introduce a multi-bit encryption scheme that relies on similar cryptographic properties of QSCDcyc.

(Image from the paper.)

Quantum Information in the Mainstream

It looks as if quantum information is starting to enter the mainstream: US News and World Report has an article on using diamonds for quantum memory.

Saturday, March 12, 2011

Classical Simulation of Quantum Adiabatic Algorithms using Mathematica on GPUs

Simulation of quantum computers is what allows us to test quantum software on a limited scale. Therefore this recent paper by Díaz-Pier, Venegas-Andraca, and Gómez-Muñoz, Classical Simulation of Quantum Adiabatic Algorithms using Mathematica on GPUs is of interest. The abstract:
In this paper we present a simulation environment enhanced with parallel processing which can be used on personal computers, based on a high-level user interface developed on Mathematica\copyright which is connected to C++ code in order to make our platform capable of communicating with a Graphics Processing Unit. We introduce the reader to the behavior of our proposal by simulating a quantum adiabatic algorithm designed for solving hard instances of the 3-SAT problem. We show that our simulator is capable of significantly increasing the number of qubits that can be simulated using classical hardware. Finally, we present a review of currently available classical simulators of quantum systems together with some justifications, based on our willingness to further understand processing properties of Nature, for devoting resources to building more powerful simulators.
(Image is figure 1 from the paper.)

More physical progress

More physical progress, out of the University of Queensland.

Wednesday, February 16, 2011

arXiv: Advances in Quantum Metrology

From arXiv: Advances in Quantum Metrology by Giovannetti, Lloyd, Maccone. It is a preliminary version, but still an intriguing topic. The abstract:

In classical estimation theory, the central limit theorem implies that the statistical error in a measurement outcome can be reduced by an amount proportional to n^(-1/2) by repeating the measures n times and then averaging. Using quantum effects, such as entanglement, it is often possible to do better, decreasing the error by an amount proportional to 1/n. Quantum metrology is the study of those quantum techniques that allow one to gain advantages over purely classical approaches. In this review, we analyze some of the most promising recent developments in this research field. Specifically, we deal with the developments of the theory and point out some of the new experiments. Then we look at one of the main new trends of the field, the analysis of how the theory must take into account the presence of noise and experimental imperfections.

(The image is figure 2 from the paper.)

Monday, February 7, 2011

arXiv: Experimental Extraction of Secure Correlations from a Noisy Private State

Recently revised on arXiv: Experimental Extraction of Secure Correlations from a Noisy Private State by Dobek, Karpinski, Demkowicz-Dobrzanski, Banaszek, and Horodecki:

We report experimental generation of a noisy entangled four-photon state that exhibits a separation between the secure key contents and distillable entanglement, a hallmark feature of the recently established quantum theory of private states. The privacy analysis, based on the full tomographic reconstruction of the prepared state, is utilized in a proof-of-principle key generation. The inferiority of distillation-based strategies to extract the key is exposed by an implementation of an entanglement distillation protocol for the produced state.

There is a short summarizing article here too:
The latest experiment with photonic entanglement, conducted by Polish physicists working in the consortium National Laboratory for Quantum Technologies, may be of vital importance to make quantum cryptography a more widespread technology. It has been demonstrated that secret communication based on quantum phenomena, which guarantees unconditional security against eavesdropping, can be also realized using sources of quantum entanglement considered until now to be too corrupt.
(Image taken from the paper.)

Tucci's take on programming

Robert Tucci has a blog on quantum computing that he's written some good things in. I strongly agree with what he wrote today and believe all of us in the field of quantum computer programming should be following:
I try to write QC programs in a platform-independent way; i.e, a way that is independent of which particular qubit realization eventually wins the grand race for a scalable QC. Whether that be anyons or any of the many other realizations currently being tried.

Wednesday, January 26, 2011

Billions of entangled particles

This has been making quite a bit of news lately, the entanglement of 10^10 spin pairs. (Image from the paper on Nature.) Here are a few different articles:

Monday, January 3, 2011

Quantum Computing Video Lectures

I'm not familiar with the author, but here's a blog post with a whole slew of quantum computing video lectures. I've seen some of them such as Deutsch's before.

Introduction to models of quantum computation and quantum programming languages

Miszczak has put together a paper, Introduction to models of quantum computation and quantum programming languages. Skimming through it, it seems to be a good overview of the subject and a quicker read than some other texts at 40 pages. While not a complete overview of quantum programming techniques, still worth flipping through. The abstract:

The goal of this report is to provide an introduction to the basic computational models used in quantum information theory. We various review models of quantum Turing machine, quantum circuits and quantum random access machine (QRAM) along with their classical counterparts. We also provide an introduction to quantum programming languages, which are developed using the QRAM model. We review the syntax of several existing quantum programming languages and discuss their features and limitations.

Quantum Computing Headlines in 2011?

Quantum computing is named one of the areas we might see breakthroughs in 2011 by this BBC article.