Method for interaction-free entanglement of quantum bits in quantum computers

1. A method for interaction-free entanglement of two quantum bits in quantum computers, in which the quantum bits to be entangled are available in a state (Ψ 44 ) with arbitrarily real phases φ and θ as an elementary quantum system, comprising:

localizing the two quantum bits ( 1 , 2 ) to be entangled in a first spatial region ( 6 ) and in a second spatial region ( 6 ′)

surrounding the first and second spatial regions ( 6 , 6 ′) by respectively one electrically switchable sheath ( 7 , 7 ′), wherein the switchable sheaths, in the activated state, completely displace a global, homogeneous magnetic field B z from the first and second spatial regions ( 6 , 6 ′), wherein, in the inactivated state, the magnetic field B z penetrates through the switchable sheaths and therefore also through the first and second spatial regions ( 6 , 6 ′), and

switching the switchable sheaths from the activated state into the inactivated state having an energy difference ΔE z while observing a boundary condition

Δ t S <t max =h /(4πΔ E z /2)

where Δt S denotes the time required for switching on the magnetic field, h denotes the Planck constant and t max denotes the maximum possible time predetermined by the energy/time uncertainty principle and, as a result of this, transferring the two quantum bits ( 1 , 2 ) into the entangled state (Ψ − ).

2. The method according to claim 1 , wherein the switchable sheaths ( 7 , 7 ′) comprise a superconductor with a jump temperature T SU and the switchable sheaths ( 7 , 7 ′) are completely superconductive in the activated state and completely normally conductive in the inactivated state.

3. The method according to claim 2 , wherein the switchable sheaths ( 7 , 7 ′) are each surrounded by an insulation layer ( 4 , 4 ′) and the insulation layers contain a resistance layer, wherein switching involves heating of the insulation layers and therefore also the switchable sheaths by the application of a short voltage pulse to the resistance layers such that the temperature of the switchable sheaths increases discontinuously over the jump temperature T SU while observing said boundary condition and wherein the switchable sheaths are, as a result of this, transferred from the activated state into the inactivated state.

4. The method according to claim 3 , wherein the insulation layers ( 4 , 4 ′) are surrounded by respectively one control layer ( 5 , 5 ′) and the control layers consist of a superconductor with a jump temperature T SS <T SU and are thermally connected to a heat sink with a temperature less than T SS , wherein a constant voltage is applied to the control layers and the voltage is selected in such a way that the temperature of the control layers stabilizes at the jump temperature T SS and, as result of this, the switchable sheaths are completely in the activated state.

5. The method according to claim 1 , wherein the utilized quantum bits are 13 C-atoms in a diamond.

6. The method according to claim 1 , wherein the utilized quantum bits are 40 Ca + -ions in the electronic ground state (4 2 S 1/2 ).

7. The method according to claim 2 , wherein the utilized quantum bits are 13 C-atoms in a diamond.

8. The method according to claim 3 , wherein the utilized quantum bits are 13 C-atoms in a diamond.

9. The method according to claim 4 , wherein the utilized quantum bits are 13 C-atoms in a diamond.

10. The method according to claim 2 , wherein the utilized quantum bits are 40 Ca + -ions in the electronic ground state (4 2 S 1/2 ).

11. The method according to claim 3 , wherein the utilized quantum bits are 40 Ca + -ions in the electronic ground state (4 2 S 1/2 ).

12. The method according to claim 4 , wherein the utilized quantum bits are 40 Ca + -ions in the electronic ground state (4 2 S 1/2 ).