In 1975 electronics pioneer Gordon Moore famously predicted that the complexity of integrated-circuit chips would double every two years. Manufacturing advances would allow the chip’s transistors to shrink and shrink, so electrical signals would have to travel less distance to process information. To the electronics industry and to consumers, Moore’s Law, as it became known, meant computerized devices would relentlessly become smaller, faster and cheaper. Thanks to ceaseless innovation in semiconductor design and fabrication, chips have followed remarkably close to that trajectory for 35 years.

Engineers knew, however, they would hit a wall at some point. Transistors would become only tens of atoms thick. At that scale, basic laws of physics would impose limits. Even before the wall was hit, two practical problems were likely to arise. Placing transistors so small and close together while still getting a high yield—usable chips versus defective ones—could become overly expensive. And the heat generated by the thicket of transistors switching on and off could climb enough to start cooking the elements themselves.

6 Comments

1. 1. robert.a.rsn 02:49 AM 12/20/09

   In the article "Quantum Computin: Superpostion of 0 and 1, you state "With superposition states, a series of electrons could represent exponentially more information than a string of silicon transistors that have only ordinary bit states." This statement implies much more information can be stored in a number of Qbits than the same number of normal bits. This is simply not true. The amount of information that can be stored in N Qbits is just N bits. In order to retrieve the information, a receiver can make only N independent up down measurements, and thus there are only 2^N possible outcomes, the same as with N normal bits.

   Reply | Report Abuse | Link to this

2. 2. kulnor 07:00 AM 12/27/09

   Robert: while you statement may be true 'after' a measurement takes place, it is incorrect as many states can co-exists before such measurement takes place and therefore during the 'processing' stage of a quantum algorithm.

   Reply | Report Abuse | Link to this

3. 3. candide 09:12 AM 1/6/10

   Of course if we progress beyond just binary, say to a base 64k (or more) states, then the number of measurements and data storage capacity are increased exponentially.
   
   Optical computing and as yet undiscovered mechanisms may make this possible.

   Reply | Report Abuse | Link to this

4. 4. Ynot56 01:51 PM 1/6/10

   Moore made his prediction in 1965 not 1975

   Reply | Report Abuse | Link to this

5. 5. robert.a.rsn in reply to kulnor 01:38 AM 1/11/10

   Kulnor:In order for information to be useful, it needs to be read by something. This means measurements have to be made by a receiver separate from the transmitter which prepared the state. There can be N independent measurements made on N Qbits. These measurements generally destroy the original state, and no more information can be obtained. Each of the N measurements can yield 1 bit, since each measurement can have one of two outcomes (for example, spin up or spin down).
   
   Suppose the Qbits are transmitted one at a time. The simplest situation is that the transmitter agrees before hand with the receiver that each Qbit will be either in the spin up or spin down state. Then clearly, only a single bit can be transmitted per Qbit.
   
   Now suppose they try to send more information. You might think the transmitter can do this by not restricting itself to spin up or spin down states. For example, it could make the spin east or north, or any direction. Each of these alternative states is a superposition of the up and down states. But the receiver can still only makes a single measurement per Qbit. For example, it could decide to make an east vs west measurement. If the transmitter happened to have polarized the Qbit spin as east or west, then the receivers measurement would agree with the transmitted spin, and a single bit would have bin successfully communicated. But suppose the transmitter had put the Qbit spin in the north, south, up, or down direction, and the receiver decided to make an east vs west measurement. Each outcome would be equally likely. The measurement gives a totally random result, and no useful information would be communicated for this Qbit. You can see the most information is obtained only when the transmitter and receiver agree on the pair of opposed directions (eg, up and down). Then one bit per Qbit can be successfully communicated. Otherwise there will be fewer bits. The same types of arguments apply even if the different Qbits are entangled. There is still 1 bit of information that can be communicated per Qbit.
   
   The transmitter could create multiple copies of the same state using multiple sets of N Qbits. Then more information could be sent. But, if there are M sets of N Qbits, then this would be NM Qbits, and at most NM bits of information can be communicated.
   

   Reply | Report Abuse | Link to this

6. 6. eco-steve 09:02 PM 3/15/10

   According to classic quantum theory it is impossible to know the state of a qubit, as reading it cause interference which changes the result. So where is the let-out clause?

   Reply | Report Abuse | Link to this