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

• US 9,443,200 B2
• Filed: 02/19/2015
• Issued: 09/13/2016
• Est. Priority Date: 05/16/2014
• Status: Active Grant

• Current Assignee: Gerhart Schroff
• Original Assignee: Gerhart Schroff
• Inventors: Schroff, Gerhart
• Primary Examiner(s): Smith, David E
• Application Number:
  US14/625,929
• Publication Number:
  US 20150332163A1
• Time in Patent Office: 572 Days
• US Class Current: 1/1
• CPC Class Codes: G06N 10/00 Quantum computing, i.e. information processing based on quantum-mechanical phenomena

Abstract

A method for interaction-free entanglement of quantum bits in quantum computers, in which the quantum bits to be entangled are available in the state Ψ₄₄ with arbitrarily real phases φ and θ as an elementary quantum system. The two quantum bits (1) and (2) are localized in spatial regions (6) and (6′) and surrounded by switchable sheaths (7) and (7′) preferably a superconductor with the jump temperature T_SU. The switchable sheaths, in the activated state, completely displace a global, homogeneous magnetic field B_z from the spatial regions (6) and (6′). In the inactivated state, the switchable sheaths do not shield the spatial regions (6) and (6′). If the switchable sheaths are switched from the activated state into the inactivated state while observing the boundary condition (R3), as a result of this, the two quantum bits (1) and (2) are transferred into the entangled state Ψ₋.

Claims

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 Δ

E_z while observing a boundary condition

Δ

t_S<

t_max=h/(4π

Δ

E_z/2)

where Δ

t_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 ¹³C-atoms in a diamond.

6. The method according to claim 1, wherein the utilized quantum bits are ⁴⁰Ca⁺-ions in the electronic ground state (4²S_1/2).

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

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

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

10. The method according to claim 2, wherein the utilized quantum bits are ⁴⁰Ca⁺-ions in the electronic ground state (4²S_1/2).

11. The method according to claim 3, wherein the utilized quantum bits are ⁴⁰Ca⁺-ions in the electronic ground state (4²S_1/2).

12. The method according to claim 4, wherein the utilized quantum bits are ⁴⁰Ca⁺-ions in the electronic ground state (4²S_1/2).