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L o g i c 1 6 U s e r M a n u a l
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3.3.3
Logic mode
This mode allows users to count the occurrence of detection patterns and to output pattern-triggered
TTL pulses. Coincidence counting is used for bell tests and other entanglement experiments. Pattern
triggered outputs are useful with gated photon detection and telecom inGaAs detectors.
Logic Patterns (Coincidence Counting)
Logic Pattern Detection events are counted when input pattern conditions are met within the
coincidence window.
The Patterns are defined by choosing each input condition to be one of:
+
active: true if the input has an active edge within the coincidence window
̶
inactive: true if the input does NOT have an active edge within the coincidence window
while there is at least one active edge on another input
Ø
ignore: true regardless of whether the input has an active edge or not
Each pattern must have a (
+
) on at least one input, otherwise it is ill-defined. Multiple patterns
can be counted concurrently on-board the unit.
The coincidence window is the maximum time from the first (
+
) detection to the last
8
(
+
) in the
pattern detection event. When all logically selected conditions (
+
,
−
,
Ø)
are met within that
time window, the event is counted. Otherwise the event is not counted.
The user can modify the coincidence window (see specifications). Ideally there will not be more
than one (+) on a single input, within one coincidence window. If this occurs, a “DoubleError” flag
will be thrown.
Examples
In the descriptions below, M is the number of effective input channels 16 (8) for configuration A (B).
An example singles event (
+
1
, Ø
2
…
Ø
M
)
is shown in Figure 3-V.a: the pattern event is counted every time
there is an active edge (
+
) on input 1, while all other inputs are ignored.
An example coincidence event (
+
1
, +
2
, Ø
3
…
Ø
M
)
is shown in Figure 3-V.b: the pattern event is counted
when both inputs 1 and 2 have an active edge within the same coincidence window.
An example anticoincidence event (
+
1
,
−
2
,
Ø
3
…
Ø
M
)
is shown in Figure 3-V.c: the pattern event is counted
when there is an active edge on input 1 but not input 2, within the coincidence window.
8
If it is a singles event, the first and last detection are one and the same
