While stepping behind the fence of a construction site, you soon feel “the wind that blows through steel and concrete carrying the ancient dampness of echoing caves” (Rozan, 1997, p. 1). About a hundred feet up and nothing between you and the high steel workers, you climb to a higher floor and see a crewmember making signs at the crane operator. There is a need for pallets of bricks, sacks of concrete, steel studs and a half-ton of mechanical equipment to be brought up in different areas. Workers from several trades are working next to, below, and above each other. Chad works on the fifth floor, he is losing his temper while putting up a vertical wall and square corners because the previous workers had not plumbed and leveled the framework appropriately. On the second floor, there is Rob, a promising young hockey player, working part time as a laborer. He has practice early in the morning and, often, games at light. He thinks about upcoming qualifications while cutting and adapting the size of several particleboards, striking with an unsharpened chisel. On the eighteenth floor, the superintendent Lukas, worried about his forthcoming retirement, hurries some ironworkers to raise three more I-beams into place; other gangs have to move quickly behind to align the holes, bolt-up, and secure the beams; it is getting dark and slippery.
Aside from the already dangerous working conditions, there is one commonality among those scenarios. These workers are creating even more hazardous environments due to personal stress. Chad must continue the work of omeone who did not pay attention. Rob may stab his own hands or someone else’s legs, or may slip or fall for not concentrating. Later, those who will put the particleboards into place may encounter further problems due to improper cuts from Rob’s unsharpened chisel. The ironworkers are exposed to a greater chance of falling before and after the tie-off of their harnesses. It may be even more dangerous for those who are positioned in the highest spots (on the vertical beam) in order to connect each incoming horizontal beam. Most ironworkers do their jobs while having to balance on 12-inch top beams each time a story is erected. According to White (1988), often the only safety net for those ironworkers is their own agility and balance.
An important goal of macroeconomic theory is to provide microfoundations for the behavioral equations used in general equilibrium models. Agents’ behavior should be based on optimization subject only to tastes and to technological constraints. This goal extends to price and wage-setting behavior. Fixing prices (or wages) and not revising them in response to shocks should also be optimal given technological constraints that make revision costly.
The “new neoclassical synthesis” in macroeconomics (a phrase coined by Goodfriend and King, 1997, henceforth NNS) has put the endogenization of price and wage setting on hold. The NNS involves using plausible exogenous nominal rigidities, with agents constrained to set prices or wages in advance, in order to explain the quantitatively important and highly persistent fluctuations of macroeconomic aggregates in response to monetary shocks that we observe in the data.
Quantum mechanical applications range from quantum computers to quantum key distribution to teleportation. In these applications, quantum error correction is extremely important for protecting quantum states against decoherence. Here I present two main results regarding quantum error correction protocols.
The first main topic I address is the development of continuous-time quantum error correction protocols via combination with techniques from quantum control. These protocols rely on weak measurement and Hamiltonian feedback instead of the projective measurements and unitary gates usually assumed by canonical quantum error correction. I show that a subclass of these protocols can be understood as a quantum feedback protocol, and analytically analyze the general case using the stabilizer formalism; I show that in this case perfect feedback can perfectly protect a stabilizer subspace. I also show through numerical simulations that another subclass of these protocols does better than canonical quantum error correction when the time between corrections is limited.
