Au Courant

This week’s au courant links:

And finally, realism in comics:

Au Courant

Show 1 footnote

  1. Badly – duh!

Belated Birthday

PLAYER KING:
I do believe you think what now you speak;
But what we do determine oft we break.
Purpose is but the slave to memory,
Of violent birth, but poor validity;
Which now, like fruit unripe, sticks on the tree;
But fall, unshaken, when they mellow be.
Most necessary ‘tis that we forget
To pay ourselves what to ourselves is debt:
What to ourselves in passion we propose,
The passion ending, doth the purpose lose.
The violence of either grief or joy
Their own enactures with themselves destroy:
Where joy most revels, grief doth most lament;
Grief joys, joy grieves, on slender accident.
This world is not for aye, nor ’tis not strange
That even our loves should with our fortunes change;
For ’tis a question left us yet to prove,
Whether love lead fortune, or else fortune love.
The great man down, you mark his favourite flies;
The poor advanced makes friends of enemies.
And hitherto doth love on fortune tend;
For who not needs shall never lack a friend,
And who in want a hollow friend doth try,
Directly seasons him his enemy.
But, orderly to end where I begun,
Our wills and fates do so contrary run
That our devices still are overthrown;
Our thoughts are ours, their ends none of our own:
So think thou wilt no second husband wed;
But die thy thoughts when thy first lord is dead.

Hamlet 3.2.182-209
Belated Birthday

Qubits

really brief, really basic primer on quantum computers: they use qubits instead of bits. Each qubit can represent a 0, a 1, or both. This last is what separates quantum computers from your average Dell or HP.

However errors can occur when a qubit holds both states: without warning they can flip to being just a regular 0 or 1, or the phase relationship can change sign (phase flip).

There are existent techniques to detect both errors, but until yesterday it was impossible to detect them both simultaneously.

Comes now some triumphant IBM researchers:

Errors are inevitable in any real information processor. Quantum computers are particularly susceptible to errors as quantum systems are highly sensitive to noise effects that can be exotic compared with the simple bit-flip errors of classical computation. As such, realizing a fault-tolerant quantum computer is a significant challenge that requires encoding the information into a quantum error-correcting code. To add to the difficulty, direct extraction of the information typically destroys the system, and ancillary syndrome systems must be employed to perform non-demolition measurements of the encoded state. Previous work in nuclei1, 2, 3, trapped ions4, 5, 6 and superconducting qubits7 has attempted to address similar problems; however, these implementations lack the ability to perform fault-tolerant syndrome extraction, which continues to be a challenge for all physical quantum computing systems.

The surface code (SC)8, 9 is a promising candidate to achieve scalable quantum computing due to its nearest-neighbour qubit layout and high fault-tolerant error thresholds10. The SC is an example of a stabilizer code12. Error detection on a lattice of code qubits is achieved through mapping stabilizer operators onto a complementary lattice of syndrome qubits, followed by classical correlation of measured outcomes. Among the syndrome qubits, a distinction is made between bit-flip syndromes (or Z-syndromes) and phase-flip syndromes (or X-syndromes). Each code qubit in the SC is coupled with two X-syndrome qubits and two Z-syndrome qubits, and, in turn, each syndrome qubit is coupled with four code qubits.

Superconducting qubits have become prime candidates for SC implementation13, 14, especially with continuing improvements to coherence times15, 16, 17 and quantum gates18. Furthermore, implementing superconducting resonators as quantum buses to realize the circuit quantum electrodynamics architecture permits a straightforward path for building connectivity into a lattice of superconducting qubits14. There are numerous ways of building the SC lattice with superconducting qubits and resonators. Here we employ an arrangement in which each qubit is coupled with two bus resonators and each bus couples with four qubits14. Although previously the engineered dissipation of a resonator has been used to stabilize the entanglement of two superconducting qubits to which it is coupled19, it is of note that here the stabilization is achieved via explicitly mapping code qubit stabilizers onto syndrome qubits.

Qubits

But of what use is a quantum computer? Well, it would be just the thing to control NASA’s new EM (electro magnetic) drive…on a ship headed to Mars:

A group at NASA’s Johnson Space Center has successfully tested an electromagnetic (EM) propulsion drive in a vacuum – a major breakthrough for a multi-year international effort comprising several competing research teams. Thrust measurements of the EM Drive defy classical physics’ expectations that such a closed (microwave) cavity should be unusable for space propulsion because of the law of conservation of momentum.[…]

The tests reported by Dr. White’s team in July 2014 were not conducted in a vacuum, and none of the tests reported by Prof. Yang in China or Mr. Shawyer in the UK were conducted in a vacuum either.

The scientific community met these NASA tests with skepticism and a number of physicists proposed that the measured thrust force in the US, UK, and China tests was more likely due to (external to the EM Drive cavity) natural thermal convection currents arising from microwave heating (internal to the EM Drive cavity).

However, Paul March, an engineer at NASA Eagleworks, recently reported in NASASpaceFlight.com’s forum (on a thread now over 500,000 views) that NASA has successfully tested their EM Drive in a hard vacuum – the first time any organization has reported such a successful test.

To this end, NASA Eagleworks has now nullified the prevailing hypothesis that thrust measurements were due to thermal convection.

NASA's EM Drive
And…speaking of Mars:

We recently updated the Mars One mission time line, with the first unmanned mission scheduled for 2020 and the first human landing on Mars in 2027. This mission is based on existing technology and the details have been well thought out with established aerospace companies. We are on our way to make the dreams of many around the world become reality. This mission to Mars will not only document the first landing on Mars but also the first settlement beyond Earth. The one-way aspect of Mars One’s mission reduces the needed infrastructure dramatically and thus makes it feasible. A return mission would require technology that is not currently available or tested and would greatly increase the cost of the mission.

Mission to Mars