Molecular crossbar latch

1. A molecular crossbar latch comprising two control wires and a signal wire that crosses the two control wires at a non-zero angle to thereby form a junction with each control wire, wherein each junction forms a switch and each said junction has a functional dimension in nanometers, with said signal wire selectively having at least two different voltage states, ranging from a 0 state to a 1 state, wherein there is an asymmetry with respect to the direction of current flow from said signal wire through one junction compared to another junction such that current flowing through one junction into or out of said signal wire can open or close, respectively, said switch, while current flowing through said other junction out of or into said signal wire can close or open, respectively, said switch, and wherein there is a voltage threshold for switching between an open switch and a closed switch.

2. The molecular crossbar latch of claim 1 wherein said switch is unconditionally opened by a voltage state on said signal wire denoted "strong 1" and is unconditionally closed by a voltage state on said signal wire denoted "strong 0", where said "strong 1" and said "strong 0" are both above threshold level.

3. The molecular crossbar latch of claim 2 wherein said switch is conditionally opened by a voltage state on said signal wire denoted "weak 1" and is conditionally closed by a voltage state on said signal wire denoted "weak 1", where said weak voltage states are less strong than said strong voltage states.

4. The molecular crossbar latch of claim 1 wherein each said junction includes a bi-stable molecule to permit switching from one state to another state.

5. The molecular crossbar latch of claim 4 wherein said bi-stable molecule permits switching between an oxidized state and a reduced state, employing an electrochemical reaction.

6. The molecular crossbar latch of claim 5 wherein said bi-stable molecule is selected from the group consisting of rotaxanes, pseudo-rotaxanes, catenanes, and spiropyrans.

7. A method for latching logic values onto nanowires in a logic array, said method comprising:

(a) providing a molecular crossbar latch comprising two control wires and a signal wire that crosses the two control wires at a non-zero angle to thereby form a junction with each control wire, wherein each junction forms a switch and each said junction has a functional dimension in nanometers, with said signal wire selectively having at least two different voltage states, ranging from a 0 state to a 1 state, wherein there is an asymmetry with respect to the direction of current flow from said signal wire through one junction compared to another junction such that current flowing through one junction into or out of said signal wire can open or close, respectively, said switch, while current flowing through said other junction out of or into said signal wire can close or open, respectively, said switch, and wherein there is a voltage threshold for switching between an open switch and a closed switch; and

(b) applying a sequence of voltages to said two control wires that results in setting said switches of said two junctions such that either said first switch is open and said second switch is closed if said signal wire has a voltage representing a logic 0, or said first switch is closed and said second switch is open if said signal wire has a voltage representing a logic 1.

8. The method of claim 7 wherein said switch is unconditionally opened by a voltage state on said signal wire denoted "strong 1" and is unconditionally closed by a voltage state on said signal wire denoted "strong 0", where said "strong 1" and said "strong 0" are both above threshold levels.

9. The method of claim 8 wherein said switch is conditionally opened by a voltage state on said signal wire denoted "weak 1" and is conditionally closed by a voltage state on said signal wire denoted "weak 1", where said weak voltage states are less strong than said strong voltage states.

10. The method of claim 7 wherein each said junction includes a bi-stable molecule to permit switching from one state to another state.

11. The method of claim 10 wherein said bi-stable molecule permits switching between an oxidized state and a reduced state, employing an electrochemical reaction.

12. The method of claim 11 wherein said bi-stable molecule is selected from the group consisting of rotaxanes, pseudo-rotaxanes, catenanes, and spiropyrans.

13. The method of claim 7 wherein said sequence of voltages has three steps:

(a) unconditionally open both said switches;

(b) conditionally close said first switch if said signal wire has a logic 1 and simultaneously conditionally close said second switch if said signal wire has a logic 0; and

(c) connect said control wire associated with said first switch to a logic 1 voltage level and simultaneously connect said second control wire associated with said second switch to a logic 0 voltage level.

14. The method of claim 7 wherein said sequence of voltages has four steps:

(a) unconditionally open both said switches;

(b) conditionally close said first switch if said signal wire has a logic 1 and leave the state of said second switch unchanged by applying a voltage on said control wire associated with said second switch that is insufficient to change its state;

(c) then conditionally close said second switch if said signal wire has a logic 0 and leave the state of said first switch unchanged by applying a voltage on said control wire associated with said first switch that is insufficient to change its state; and

(d) connect said control wire associated with said first switch to a logic 1 voltage level and simultaneously connect said second control wire associated with said second switch to a logic 0 voltage level.

15. A method for restoring a weakened voltage value of a signal to its full value in a nano-scale switch, said method comprising:

(a) providing a molecular crossbar latch comprising two control wires and a signal wire that crosses the two control wires at a non-zero angle to thereby form a junction with each control wire, wherein each junction forms a switch and each said junction has a functional dimension in nanometers, with said signal wire selectively having at least two different voltage states, ranging from a 0 state to a 1 state, wherein there is an asymmetry with respect to the direction of current flow from said signal wire through one junction compared to another junction such that current flowing through one junction into or out of said signal wire can open or close, respectively, said switch, while current flowing through said other junction out of or into said signal wire can close or open, respectively, said switch, and wherein there is a voltage threshold for switching between an open switch and a closed switch;

(b) latching said signal by applying a sequence of voltages to said two control wires that results in setting said switches of said two junctions such that either said first switch is open and said second switch is closed if said signal wire has a voltage representing a logic 0, or said first switch is closed and said second switch is open if said signal wire has a voltage representing a logic 1; and

(c) placing a voltage representing logic 1 on said first control wire and a voltage representing logic 0 on said second control wire.

16. The method of claim 15 wherein said switch is unconditionally opened by a voltage state on said signal wire denoted "strong 1" and is unconditionally closed by a voltage state on said signal wire denoted "strong 0", where said "strong 1" and said "strong 0" are both above threshold level.

17. The method of claim 16 wherein said switch is conditionally opened by a voltage state on said signal wire denoted "weak 1" and is conditionally closed by a voltage state on said signal wire denoted "weak 1", where said weak voltage states are less strong than said strong voltage states.

18. The method of claim 15 wherein each said junction includes a bi-stable molecule to permit switching from one state to another state.

19. The method of claim 18 wherein said bi-stable molecule permits switching between an oxidized state and a reduced state, employing an electrochemical reaction.

20. The method of claim 19 wherein said bi-stable molecule is selected from the group consisting of rotaxanes, pseudo-rotaxanes, catenanes, and spiropyrans.

21. The method of claim 15 wherein said sequence of voltages has three steps:

(a) unconditionally open both said switches;

(b) conditionally close said first switch if said signal wire has a logic 1 and simultaneously conditionally close said second switch if said signal wire has a logic 0; and

(c) connect said control wire associated with said first switch to a logic 1 voltage level and simultaneously connect said second control wire associated with said second switch to a logic 0 voltage level.

22. The method of claim 15 wherein said sequence of voltages has four steps:

(a) unconditionally open both said switches;

(b) conditionally close said first switch if said signal wire has a logic 1 and leave the state of said second switch unchanged by applying a voltage on said control wire associated with said second switch that is insufficient to change its state;

(c) then conditionally close said second switch if said signal wire has a logic 0 and leave the state of said first switch unchanged by applying a voltage on said control wire associated with said first switch that is insufficient to change its state; and

(d) connect said control wire associated with said first switch to a logic 1 voltage level and simultaneously connect said second control wire associated with said second switch to a logic 0 voltage level.

23. A method for inverting the logic value of a signal in a nano-scale switch, said method comprising:

(a) providing a molecular crossbar latch comprising two control wires and a signal wire that crosses the two control wires at a non-zero angle to thereby form a junction with each control wire, wherein each junction forms a switch and each said junction has a functional dimension in nanometers, with said signal wire selectively having at least two different voltage states, ranging from a 0 state to a 1 state, wherein there is an asymmetry with respect to the direction of current flow from said signal wire through one junction compared to another junction such that current flowing through one junction into or out of said signal wire can open or close, respectively, said switch, while current flowing through said other junction out of or into said signal wire can close or open, respectively, said switch, and wherein there is a voltage threshold for switching between an open switch and a closed switch;

(b) latching said signal by applying a sequence of voltages to said two control wires that results in setting said switches of said two junctions such that either said first switch is open and said second switch is closed if said signal wire has a voltage representing a logic 0, or said first switch is closed and said second switch is open if said signal wire has a voltage representing a logic 1; and

(c) placing a voltage representing logic 0 on said first control wire and a voltage representing logic 1 on said second control wire.

24. The method of claim 23 wherein said switch is unconditionally opened by a voltage state on said signal wire denoted "strong 1" and is unconditionally closed by a voltage state on said signal wire denoted "strong 0", where said "strong 1" and said "strong 0" are both above threshold level.

25. The method of claim 24 wherein said switch is conditionally opened by a voltage state on said signal wire denoted "weak 1" and is conditionally closed by a voltage state on said signal wire denoted "weak 1", where said weak voltage states are less strong than said strong voltage states.

26. The method of claim 23 wherein each said junction includes a bi-stable molecule to permit switching from one state to another state.

27. The method of claim 26 wherein said bi-stable molecule permits switching between an oxidized state and a reduced state, employing an electrochemical reaction.

28. The method of claim 27 wherein said bi-stable molecule is selected from the group consisting of rotaxanes, pseudo-rotaxanes, catenanes, and spiropyrans.

29. The method of claim 23 wherein said sequence of voltages has three steps:

(a) unconditionally open both said switches;

(b) conditionally close said first switch if said signal wire has a logic 1 and simultaneously conditionally close said second switch if said signal wire has a logic 0, and

(c) connect said control wire associated with said first switch to a logic 0 voltage level and simultaneously connect said second control wire associated with said second switch to a logic 1 voltage level.

30. The method of claim 23 wherein said sequence of voltages has four steps:

(a) unconditionally open both said switches;

(b) conditionally close said first switch if said signal wire has a logic 1 and leave the state of said second switch unchanged by applying a voltage on said control wire associated with said second switch that is insufficient to change its state;

(c) then conditionally close said second switch if said signal wire has a logic 0 and leave the state of said first switch unchanged by applying a voltage on said control wire associated with said first switch that is insufficient to change its state; and

(d) connect said control wire associated with said first switch to a logic 0 voltage level and simultaneously connect said second control wire associated with said second switch to a logic 1 voltage level.