Fictional technology is an umbrella term for technological processes and devices that don't exist in reality, proposed or described in many different contexts:
Exploratory engineering seeks to identify if a prospective technology can be designed in detail, and simulated, even if it cannot be built yet - this is often a prerequisite to venture capital funding, or investigation in weapons research.
Propaganda often emphasizes a speculative potential of a specific technology in order to stimulate investment in it, or a counter-technology. This is a common motivation in any society dominated by a military-industrial complex. See also militarism, technological escalation, arms race.
Advertising which emphasizes some amazing potential of some technology that is "under development" (usually without any specific timelines) by a company that is seeking simply to present itself as being competent with technology. See also vaporware, persuasion technology.
Science fiction and fantasy which explores the social or political or personal impact of some technology through storytelling.
List of emerging technologies a more serious field.
Examples of such fictional technologies are:
Anti-gravity
Artificial womb
Dyson sphere, Matrioshka brain
Force field, a barrier made up of energy or particles to protect as a shield or wall.
Mind uploading
Reversible cryonics
Simulated reality
Nuclear damper
Molecular assembler, Universal constructor
Faster-than-light Travel, Warp drive
Tachyonic antitelephone
Terraforming
Time travel
Space elevator or Skyhook, although Google was revealed to be working on plans for a space elevator at its secretive Google X Lab location.
Star lifting
Tractor beam
Transporter
Many technologies were fictional for a long time before they became real, such as:
Atomic bomb
Artificial intelligence
Expert system
Biochemical engineering
Biomedical engineering
Genetic engineering
Hypertext, e.g. the World Wide Web
Radiological weapon
Mobile phones
Quantum computer
Rocket pack
Videoconferencing
Spaceflight
There are also technologies that have been proven to work beyond question, but currently are not practical given the alternatives, i.e. there is a more appropriate technology for that purpose:
General purpose robots (only economically feasible with rather drastic energy and material subsidy, or in extremely hazardous applications that, arguably, no one should really be doing at all). However, note that specialized robots are widely used in industrial production.
death ray (there are easier methods of execution)
jet pack (as yet impractical)
antimatter weapon (with current technology, antimatter cannot be produced in sufficient quantities to be used as weapons)
Proposals for further development of these are thus more and more likely to be seen as fictional, misleading or amusing. Robot toys for instance have become popular. One could argue that the atomic bomb, given the consequences of its use, also belongs in this category.
